Despite its outrage over the reported Soviet downing of its passenger jet, South Korea is attempting to keep on track its policy of opening up more diplomatic relations with the Soviet Union.

Out of the shock of the disaster have come two seemingly contradictory reactions.

On the one hand, the government is orchestrating large-scale, anti-Russian demonstrations at home and waging a major campaign abroad to encourage friendly countries to condemn the Soviet missile attack on a Korean Air Lines jet last Thursday morning Seoul time.

But it is also hoping to keep the door open for more Soviet contacts, a policy that had begun to bear fruit in the past two years.

"Our open-door policy has a long history and there is good reason to continue that policy," Foreign Minister Lee Bum Suk told reporters here today.

At a news conference, he virtually ruled out independent retaliatory action against the Soviet Union and considerably softened language he had used earlier hinting at a possible revision of the open-door policy.

It has been a major foreign policy goal of this country for several years to encourage contacts with Moscow, even though the Russians provide military support to the communist regime of North Korea.

No direct diplomatic relations exist between the two countries, but South Korea has sent delegations to international meetings in the Soviet Union and last year the Soviets began to reciprocate.

Three Russian journalists attended a convention of Asian journalists here last year and a Russian museum director arrived for an archeology meeting.

The government here views such visits as important steps in its effort to obtain international recognition. North and South Korea wage an unending struggle for the attentions of other countries and lately South Korea has seemed to be winning.

Next month the International Parliamentary Union will meet in Seoul and its convening here is a clear victory over Pyongyang, which had pulled out all diplomatic stops to block it. The Soviets have neither accepted nor rejected their invitation for that meeting.

Seoul will also host the Asian Games in 1986 and the Olympic Games in 1988, two events that will widen its advantage over Pyongyang as a world capital.

In the first days after the airliner was downed, it appeared the government would abandon its policy of pressing for Soviet contacts. South Korea canceled the plan to send a delegation to the UNESCO meeting on international communications at Tashkent in the Soviet Union. Foreign Minister Lee told the National Assembly the airline disaster meant he would have to reexamine the open-door policy toward Moscow.

Today, however, Lee told reporters he has not made up his mind whether to reexamine that policy and indicated his decision will be determined by future Soviet reactions to the tragedy.

Lee also said South Korea is not considering any independent retaliatory action, conceding that it has only "limited capacity" to act in any hostile way toward the Soviet Union.

One outspoken member of the South Korean National Assembly, Lim Thok Kyu, urged the government today to blockade the Korea Strait, a narrow stretch of water between the southern port city of Pusan and the Japanese island of Tsushima. The strait is used extensively by Soviet warships based in Vladivostok.

The foreign minister said there is "no such plan" to block the strait.