Two weeks ago, wallposters and cartoons criticizing local government actions covered Canton's "Democracy Wall" along a busy shopping avenue. Now the wall is empty, except for a freshly painted notice: "Post no bills, by order of city public security."

A nationwide damper on free expression, while limiting prodemocracy wallposters to certain areas in Peking, has almost completely eliminated them from other major Chinese cities such as this huge southern port and the major industrial center, Wuhan, a tour of the cities reveals.

Posters also dissappeared overnight April 5 from the downtown area of Chongqing (Chungking) in the southwest and notices with that same date are now found everywhere in Canton warning against voicing "opposition to socialism."

As police arrest some vehement government critics in Peking, while letting critical posters stay up in other cities like Kunming in the far crackdown against a five-month-old democracy movement proceeds by fits and starts. Everywhere, however, it appears to have dampened Chinese interest in talk about political subjects and reestablished the sort of personal paranoia many Chinese had claimed was washed away by the outpouring of democratic sentiment last November.

"I just don't want to talk about Chairman Mao," said one friendly worker with a nervous smile after striking up a conservation with a foreign visitor on a street in Kunming. "And, please don't tell anyone you were talking to me."

In Kunming, like some outlying parts of Chongqing and along Peking's now-famous Democracy Wall, wallposters are still tolerated. But in local newspaper articles and in public notices in Kunming and Canton, stern warnings about public expression have created an unease about contacts with foreigners that is having a considerable effect on Westerners who meet ordinary Chinese.

A group of students who took two American visitors on an impromptu tour of the Kunming zoo earlier this month suddenly became agitated and eager to leave when they spotted a Chinese man with a camera. Later, the Americans talked to the man, who said he was merely a worker from another city, in Kunming on a sightseeing trip.

The new crackdown is soft and insubstantial compared to China's last great turn against dissent in the aftermath of the campaign of 1957 to "let a hundred flowers bloom." Then, thousands of intellectuals and local leaders were sent to labor camps because they responded too enthusiastically to Chairman Mao's call for critism of government policies.

Today's wallposter authors and the dissidents recently apprehended in Peking are mostly young people or long-time unemployed. Older intellectuals who spoke out in the 1950s are apparently content now to concerntrate on their work in what remains the relatively relaxed official atmosphere of the post-Mao era.

In some areas I visited in the past two weeks, however, the crackdown apparently has been harsh enough to frighten people and make them wonder how much further it might go. The new restrictions here appear to be designed in part to discourage local residents who might try to catch the attention of thousands of foreigners coming for the semiannual trade fair.

On nearly every Canton block, a notice dated April 5 has appeared, with warnings against disruptive demontrations, scolding of public officials and other acts that have occured in several parts of China in recent weeks. One warning says: "Wallposters...that oppose socialism, the dictatorship of the proletariat, the leadership of the Communist Party, Marxism, Lenishm, Mao Tsetung thought, or which betray national secrets or violate the constitution and the law...are not permitted."

April 5 is, ironically, the anniversary of a major spontaneous, antigovernment demonstration in Pekng's Tienanmen Square in 1976. It was suppressed, and then declared a revolutionary event last November, signaling the beginning of relaxed restrictions on the prodemocracy wallposter campaign.

On March 30, a long wall across from Canton's Nanfang department store and next to a major bus stop was covered with posters. The poster writers had labelled the spot "Cantonhs Democracy Wall" in large characters.

Many of the posters complained about punishment some city workers had suffered in 1977 for a poster they had put up three years earlier. Wednesday, all the posters were gone, and I could fine no others in a trip through the city's main streets.

In Wuhan, the capital of Hupei province and central China's major industrial city, citizens questioned on the streets said a popular wall along the central shopping street, Zhongshanlu, had been stripped of posters. A group of youths on a street corner told an American visitor Monday night that the posters were removed in late March by the Public Security Bureau, the local police.

Wuhan for several months hads a vigorous wallposter campaign. City residents called for freedom to hold meetings to discuss changes in the constitution and for the reversal of verdicts against the victims of past purges in the city.

"Did you think the wallposters were good or bad?" one youth was asked.

"Well, that means do I think democracy is good or bad, and I'm not really clear on that," he said.

A tour of other major Wuhan shopping areas turned up only one small poster. It was unsigned and undated, written by a rural workers from a landlord family who asked that official persecution of people with unfavorable class backgrounds be eneded so that he could marry and leads a normal life.

In Chongqing, a number of wallposters and underground newspapers pasted on walls near the Chongqing department were washed off the walls April 5 by two men using a water hose and a scrub brush. They also removed a parent's appeal for help in finding a missing three-year-old girl and a poster criticizing the egotism of poster writers.

Wallposters at a major bus terminus near Datian Bay stadium on the outskirts were still on display early April 6, however.

A local official, asked about the poster removal, said, "There are no restrictions on posters. We just have to keep the city looking clean."

That appeared to echo the sentiments of a leading Peking official, Liu Jianfu, who said March 29: "Sticking up wallposters is a democratic right of the masses. However, sticking up posters everywhere, writing and drawing in an indiscriminate way, and even sticking them on the reviewing stand and memorials in Tienanmen Square causes a great mess, which makes people avert their eyes, spoils the appearance of the city and adversely affects traffic order."

Agence France-Presse has reported between 30 and 40 wallposter activists picked up for questioning in Peking in the last several days.

Recent visitors to Peking reaching here said Chinese officials said have denied those figures, although one French correspondent said he personally saw two wallposter authors arrested early one morning.

The dissidents have been calling for a change from Communist Party leadership, a forbidden subject under the new rules.

Peking authorities have washed away all wallposters on the city's main shopping avenue, Wangfujing Street, but left up hundreds of posters on Democracy Wall on the Avenue of Eternal Peace. CAPTION: Map, no caption, By Dave Cook-The Washington Post