TOKYO--Leaders of the industrialized democracies ended a "smooth summit" yesterday, voicing satisfaction that they confronted terrorism while moving toward new trade talks and a revamped world monetary policy--two principal goals of the economic conference.

Although the United States, Britain, Canada, France, Japan, Italy and West Germany failed to come to grips with the divisive and volatile issue of farm export subsidies, they did agree to a host of other initiatives, including coordinated efforts to improve nuclear safety in the wake of the Chernobyl reactor accident in the Soviet Union.

But for world leaders newly committed to fighting terrorism, the summit closed on the same raucous note that marred its opening: Japanese radicals seeking to sabotage the proceedings descended on subway and train stations with smoke bombs packed with firecrackers, crippling rush-hour traffic, but claiming no casualties, in a city turning weary under a welter of unprecedented security restrictions.

And for President Reagan, there came a threat from Palestinian radical Abul Abbas, in a broadcast report, to target America for terrorist attacks.

"Let him try," Reagan declared, responding to reporters' questions.

The president's top aides declared that the Reagan administration had come away from the summit with much of what it had sought, including a statement of unity against terrorism, which singled out Moammar Khadafy's Libya "inparticular."

Britain's Prime Minister Margaret Thatcher declared "mission accomplished." U.S. Treasury Secretary James A. Baker said, "It was a smooth summit." West German Chancellor Helmut Kohl proclaimed: "We were able to achieve good results." And Italian Prime Minister Bettino Craxi said he came away from the summit gathering "with full satisfaction."

In saying the summit was a success for Reagan, the president's top aides cited acceptance of Baker's plan to try to stabilize currency exchange rates through a system of economic checks and balances and an agreement by the other summit partners to back preliminary talks in September aimed at lowering barriers that restrict U.S. sales abroad.

Reagan was to return to Washington on today, with only a refueling stop in Anchorage, Alaska, concluding the more than 22,000-mile, 13-day Far Eastern tour, the longest out-of-town trip of his more than five-year presidency.

Officials revealed that as a follow-up to the talks here, Reagan will send several of his top aides across Asia to report to other governments on his economic talks here. Secretary of State George P. Shultz, for instance, will fly to Seoul to see President Chun Doo-hwan of South Korea and go from there to Manila for further discussions with President Corazon Aquino.

But on the question of how specifically to cope with terrorism, Reagan acknowledged that the three day summit did not bring all he'd hoped for. Lingering differences among the summit nations over counter-terrorist strategy surfaced on the conference's final day.

While the summit leaders earlier had approved a tough anti-terrorist statement singling out Libya as a state which sponsors terrorism, Japanese Prime Minister Yasuhiro Nakasone emphasized there was no mention of sanctions.

One of the most notable and unresolved disputes involved farm subsidies. The Reagan administration has been cutting subsidies at home and would like to see a commitment from European nations to do the same. The Europeans are cool to the proposal and the leaders agreed only to study the issue.

In a shift in monetary policy engineered by Baker, the leaders agreed to try to stabilize currency exchange rates through a system of economic checks and balances.

The plan, designed to avoid wild fluctuations on currency markets, would affect the U.S. dollar, the yen, the West German mark, French franc and the British pound.

As the annual session closed, the dollar plunged to another post-World War II low against the yen, a disappointment to Japanese businessmen.