Taiwan announced plans today to increase military spending, which already consumes about 40 percent of its national budget, and develop a new array of weapons following the U.S. pullout from the island.

The Taiwan garrison command, the military's internal security agency, also announced intensified moves against communist subversion, creating speculation here that the American pullout also could lead to a crack-down on non-communist dissent.

New military limits on civil rights, caused by uneasiness over the island's growing diplomatic isolation, could increase tension as the United States and Taiwan maneuver to develop a new, unofficial relationship.

At an emergency meeting of the ruling Nationlist Party's Central Committee, Premier Y.S. Sun said, "We will boost our defense budget to . . . step up procurement of modern weapons and strengthen our capability to make major weapons, develop new types of naval vessels, mines, heavy artillery and long-range missiles so that we can establish a self-substaining defense industry."

The announcement of increased defense spending accompanied a continuation of the anti-U.S. sentiment that has poured forth here since Peking and Washington announced their intention to normalize relations.

At the Central Committee meeting, President Chiang Ching-kuo said Washington had "ushered a wolf into its living room. This is certainly an unwise, horrible move."

Although barbed wire barricades remained up around the U.S. Embassy building today, there was no repeat of Saturday's anti-American demonstrations. Most embassy staff staved home today, but an American official said all employees were told to report for work Tuesday.

The Carter administration, in revealing its decision to recognize mainland China and cut official ties with Taiwan, sought to calm fears of a military attack from the mainland by promising that American defensive arms would still be made available to this island of 17 million people.

Fearing reports of improvements in Peking's air force, Taiwan has almost completed the deployment of about 200 Northrop F5E fighters, according to military sources here. The army also has designed and built its own surface-to-surface tactical missile, the Hsiung Feng, displayed for the first time at a military parade in October.

Peking does not appear to have the equipment or trained manpower for an invasion of the island, but military analysts say Taiwan may be vulnerable to a navel blockade by China's estimated 75 submarines and 23 major surface combat vessels. Taiwanese authorities are antisubmarine sources, including the purchase of more helicopters and sonar equipment.

The best guarantee of Taiwan's security, however, remains its fast-growing industry, the prosperity and firm anticommunism of its population and China's preoccupation with military threats from the Soviet Union on its northern border and Vietnam on its southern border.

To the Taiwanese, the most serious immediate threat appears to be espionage by communists agents on the island, a problem whose magnitude is difficult to determine.

Taiwan must allow relatively free access to overseas Chinese businessmen as they provide the greatest amount of foreign investment in the island and help maintain vital commercial ties with dozens of nations that no longer officially recognize the government here. A few of these businessmen are though to be Communist agents seeking to set up information and sabotage networks on the island.

The Taiwan garrison command announced after the U.S. pullout was revealed that it had tightened surveillance on coastlines and airports and increased its "crackdown on agents," even though no arrests have been announced. Over the last few years, the command has jailed several noncommunist dissidents.

At the Central Committee meeting Chiang said "any speeches or conduct" endangering the anticomunist policies of the country would be "eliminated," according to a record in the semiofficial press. Chiang's remarks seemed directed in particular at Taiwanese who have called for the island to declare its formal independence from China and give up the nationalist dream of retaking the mainland.

"Anyone talking of an independent Taiwan is betraying his country and people," Chiang said. "We will not allow talk, organizations or actions like that to exist on this bastion."

Legislative elections scheduled for Dec. 23 have been postponed indefinately and Taiwanese interviewed today said they were willing to accept some new limits on democratic debate in the interests of unity.

"Before normalization, we had to be concerned with what the Americans though about human rights, but now we don't have to pay attention to that," said Kuang-hsing Chen, a university senior.

"We still care about human rights," said John Han, international news director for a business publication here, "but now we can say, 'don't interfere in our internal affairs.'"

Taiwan must be assured of a regular supply of spare parts for the American weapons it has purchased over the years. Doubts about long-term supply of such parts from Israel was one reason for the government recently turning down a deal to buy Israel Kfir C2 fighters.

Sources here said the United States has agreed to sell about $138 million in arms to Taiwan this year, with most of the equipment yet to be delivered. Premier Sun's call for the development of new weapons reflected concern over China's current push to moderize its own armed forces, with purchases of equipment like the vertical takeoff Harrier jet and development of a new fighter built around the Rolls Royce Spey engine.

"Taiwan like any prudent nation must plan now for the weapons systems that it will use to defend itself in the mid-1980s," said one local observer.

The government requires all healthy males to serve at least 22 months in the armed services. At the moment, the island has about 500,000 active duty servicemen and a ready reserve of more than one million.Once or twice a year television stations will broadcast the signal for a call-up drill which allows the army to test its ability to bring the reserve into action in 48 hours.

Military experts say a successful amphibious assault by China against Taiwan would, under the usual formulas, require three times as many troops as Taiwan has. The total forces of China's People's Liberation Army, including the million or so troops committed to defense of the Soviet border, number about 3.5 to 4 million.

Analysts say they expect both the Chinese on the mainland and the Taiwanese here to watch for significant signs of the extent of U.S. military involvement after the remaining 600 to 700 U.S. servicemen are withdrawn in four months.

About $36 million in U.S. military stocks, mostly petroleum and ammunition, remain here and could be turned over to the Taiwanese. If Washington approved, the U.S. Navy would gladly continue to use Taipei as a convenient and popular liberty port for sailors who can no longer afford the prices in Japan.