President Reagan's new measures against Libya are likely to have only limited effect on the policies of Libyan leader Muammar Qaddafi, according to experts familiar with the efforts by this and previous administrations to pressure other nations through the imposition of economic sanctions.

"We resort to sanctions mostly to satisfy our own public opinion and convince ourselves that we are doing something" when stronger measures -- such as military action -- would be too risky or counterproductive, said Lloyd N. Cutler, who as White House counsel was an architect of President Jimmy Carter's economic sanctions against Iran after the 1979 seizure of U.S. hostages.

Cutler said economic sanctions usually have "a more salutary effect on our public" than on the policy of the nation being pressured, and that this is likely to be the case with the sanctions on Libya. "They will have virtually no effect" beyond short-run dislocations, he predicted.

Lionel H. Olmer, who was undersecretary of commerce for international trade in 1981-85, said the Libya sanctions, like those against South Africa, appear to have been put into place for mostly political reasons.

Some sanctions are put into place "with the knowledge that they will have limited economic impact" but because the United States wishes to make a statement of importance to the public, Olmer said. Such sanctions for foreign policy reasons "can be disruptive in the short run when used selectively and where the United States has leverage," he said, adding that "over the long term I know of no instance where they have been effective."

The Reagan administration has ordered economic sanctions against six countries: the Soviet Union and Poland (mostly because of the imposition of Soviet-backed martial law in Poland), Libya, Nicaragua, Iran and South Africa. Many of the sanctions against the Soviet Union and Poland were later removed as U.S.-Soviet relations improved and as the imposition of martial law became a more distant memory.

The initial Libya sanctions of December 1981 were imposed because of reports that Libyan terrorist teams had been dispatched to attack Reagan and other senior officials in the United States. In taking the new measures this week, administration officials said the earlier steps had only limited effect.

"Despite sanctions that were in place, both merchandise trade and service contracts were bringing Americans into expanded commercial exchanges" with Libya, a senior State Department official said at the White House Tuesday night.

The Nicaragua sanctions, including a trade embargo, were imposed in response to suggestions from members of Congress, who objected to approving aid to rebels fighting the government in Nicaragua unless all other possible U.S. measures had been exhausted.

Many observers, including a number of administration officials, have said the economic measures have had little or no effect on Nicaraguan policy.

The sanctions against South Africa were imposed by executive order to forestall congressional passage of tougher measures over administration objections. Prior to Reagan's shift on the issue last September, Secretary of State George P. Shultz described boycotts, embargoes and sanctions against South Africa as "ineffectual actions that are more likely to strengthen resistance to change than strengthen the forces of reform."