Vietnamese troops, tanks and artillery paraded through the streets here today to celebrate the 10th anniversary of the Communist victory in Saigon.

The Vietnamese leadership hailed the capture of the former South Vietnamese capital as "a brilliant exploit of the 20th century" and a national turning point.

About 10,000 soldiers -- including medal-bedecked officers, infantry with bayonets fixed, radio operators and militiamen with U.S.-made M16s -- goose-stepped past dignitaries including Communist Party Secretary Le Duan, Premier Pham Van Dong and President Truong Chinh.

They marched down April 30 Avenue in front of the former South Vietnamese presidential palace as tens of thousands of organized spectators from various city neighborhoods watched in tree-lined Reunification Square next to the Saigon cathedral.

Helicopters and MiG jet fighters flew overhead.

The troops were followed by about 40,000 civilians representing various state-run enterprises and organizations.

Crowd reaction was muted, and many spectators drifted away from the parade soon after putting in their obligatory appearances in groups organized by neighborhood committees. In the rest of the city the holiday appeared to be marked by business as usual. The black market was busy, and many residents appeared to pay little attention to the celebrations.

The display of troops and equipment and the parade of civilians was meant to underscore Vietnam's military strength and civilian solidarity with the "reunification" of the country. It was covered by 200 foreign journalists, including live broadcasts by two American television networks.

The parade capped eight weeks of celebrations of what the Ho Chi Minh City Communist Party chief called "the total collapse of America's neocolonialist regime in the south, putting an end to a 100-year-old slavery existence in our city."

In a keynote speech, Nguyen Van Linh, also a member of the ruling Politburo, struck a theme of major concern to the Hanoi authorities. He noted that the Americans left behind "a messy and confusing situation" and lamented that "the reactionary and depraved neocolonialist culture that has spoiled part of the youth and teen-agers remains the most acute and persistent danger."

But the speech, while condemning the U.S. role in the Vietnam War, contained relatively mild rhetoric about the United States. There was no reference to current U.S. policies or the Reagan administration, apparently in keeping with Hanoi's policy of seeking an opening to Washington in hopes of establishing diplomatic relations.

The capture of this city by Communist forces on April 30, 1975, after a 55-day offensive in the south climaxed 30 years of warfare in Vietnam and realized the late Ho Chi Minh's dream of uniting the country. It also marked the first American defeat in a war and left scars that are still healing in both nations.

Spearheaded by tanks, about 100,000 North Vietnamese troops drove almost unopposed into the city on that day 10 years ago, only hours after a panicky and chaotic American evacuation.

Fearful of bloody reprisals, thousands of South Vietnamese soldiers and civilians struggled desperately to get out with the final American helicopter airlift. Angry mobs looted abandoned U.S. installations, and deserting Saigon government troops shed their uniforms and weapons.

In their hasty exodus, the Americans left behind vast quantities of equipment -- including aircraft that are still being cannibalized by Vietnamese Air Force mechanics -- and thousands of local residents who worked for U.S. offices.

Some today still sidle up to visiting Americans and plead for help in getting out. Much rarer are those, like a former officer in a South Vietnamese ranger battalion, who told visitors defiantly, "One day we'll be back."

Among those evacuated 10 years ago were about 5,000 Americans and about 50,000 Vietnamese, including most of the South Vietnamese Army's top officers and top Vietnamese officials. In the next few days, 70,000 more Vietnamese fled by boat to U.S. ships off the coast.

Left behind was a last-ditch government under Gen. Duong Van (Big) Minh, who surrendered to a North Vietnamese colonel the morning of April 30, 1975, after a tank-led unit crashed through the gates of the presidential palace.

The colonel, Bui Tin, who was a correspondent for Hanoi's Army newspaper but took the surrender because he was the ranking officer in the unit, recalled that "everywhere there were Saigon soldiers without uniforms, their torsos bare."

In an interview in Hanoi recently, he told how he walked into a large salon on the second floor of the palace where Minh and about 30 ministers, senators and military officers were assembled.

"We have been waiting for you here since morning to transfer power," Bui Tin quoted Minh as saying. The colonel said he replied, "There's no question of transferring power. All your power has been destroyed. You cannot give what you do not have."

Then, Bui Tin said, firing erupted outside and officials hit the floor. "I told them, 'Stay calm. There's no danger. It's only our soliders shooting in the air to celebrate. The war is over.' "

Bui Tin said he told them that if they had any "nationalist spirit," they would celebrate too, since "the victory belongs to all the Vietnamese people."

Many Saigonese, relieved that the war was finally over, initially did welcome what Hanoi called the "liberation" of the city. But many, including some southern Communists of the Vietcong guerrilla forces that participated in the long struggle, soon came to regard the northern troops and commissars as conquerors as the grim realities of Hanoi-style Communist rule set in.

The feared bloodbath did not happen here. But tens of thousands of former South Vietnamese officers, troops and civilian officials were sent to "reeducation" camps for long periods, and nearly 1 million refugees fled the country.

Today, as Vietnamese authorities bask in the faded afterglow of their 1975 victory, the emphasis is on the government's achievements of the past 10 years and the need for further efforts.

Since 1975, this "former consuming city full of social evils, scoundrels and prostitutes" has been transformed "into a producing city of working people . . . living together in love and justice," the Ho Chi Minh City people's committee said in a statement. "The revolution has transformed, reeducated an even used former offenders. The new regime has rehabilitated human dignity and brought about happiness for everyone."

In recent days, however, the government's idea of transformation has included rounding up street urchins, among them a number of Amerasians, who used to hang out near hotels frequented by foreigners and beg for money or help in leaving the country. According to children who evaded the dragnet, some were "arrested" and placed in a juvenile detention center at least temporarily to keep them out of the way during the anniversary celebrations.

Main streets also have been largely cleared of the homeless poor who could be seen nightly earlier this month sleeping on sidewalks and in doorways in the largest city of what authorities call "the first peasants' and workers' state in Southeast Asia."

But even before those cosmetic moves, the Communists had made this city of 3.5 million people cleaner and safer than it was before 1975. Foreigners returning for the first time since then are struck by the relative absence of the garbage, the pollution, the prostitutes and the hustlers of all description of wartime Saigon.

Gone are the bars and brothels and the raucous nightlife, replaced by tame, state-owned cafes and handicraft shops. The former Maxim's nightclub on Tu Do Street now features a motley band including electric guitars, violins and a cellist that plays an assortment of tunes while slides of Soviet and Eastern European cities are projected on the wall behind it.

The Rex Hotel, once the site of an American officers' club, now has a state-owned disco advertised by a huge marquee in English and featuring a live band twice a week. Slender Vietnamese women take to the dance floor for a small sum with burly Russians, then disappear by 11 p.m. when the place closes.

Despite the changes instituted by the Communist government, there are signs in the former South Vietnam of a "passive resistance" to the "socialist transformation" policy of the north. This former capital is a particularly stark symbol of the tension between the north and the south.

Compared to dreary Hanoi, this city is still like the lively, freewheeling capital of a different country. But compared to the Saigon of old, many returning former residents find it sad and depressing.