The carefully limited steps announced by President Reagan last night in reaction to the Soviet Union's shooting down of Korean Air Lines Flight 007 are unlikely to affect Soviet-American relations in major fashion and hold out only modest promise for future international efforts to affect Soviet air defense practices.

Reagan's words of condemnation were strong, but his actions were notably less ambitious than those of President Carter after the Soviet invasion of Afghanistan or even of Reagan following the imposition of martial law in Poland.

This time, the retaliatory steps announced by the U.S. president were limited almost entirely to matters related to the incident itself, such as demands for apology and reparations to the families of those who perished, or to closely related questions, such as requests for international cooperation in penalizing or isolating Soviet civil aviation. There was no indication last night that such efforts are likely to succeed, and indeed no statement from the administration that success is expected or essential.

In other dealings with the Soviets, the administration is proceeding with policies and plans that had been in motion well before the incident, in some cases with temporary adjustments to take account of the current anger.

Ambassador Paul H. Nitze returned to Geneva over the weekend to resume Euromissiles negotiations with his Soviet opposite number, although administration sources said it had been decided last Saturday, in part due to the airliner case, that Nitze will not modify the existing U.S. negotiating posture in the early weeks of the renewed talks.

Similarly, Secretary of State George P. Shultz is to depart today for Madrid, where he is scheduled to meet with Soviet Foreign Minister Andrei A. Gromyko Thursday on the occasion of the ceremonial conclusion of new East-West arrangements flowing from the 1975 Helsinki accords.

The meeting had been expected to seek paths toward agreement on a wide range of issues, but Reagan said last night that Shultz intends to use his talk with Gromyko to discuss the Korean airliner incident.

Reporters were told in a White House briefing that this question will be "the principal focus" of the highest level U.S.-Soviet discussion in almost a year.

Shultz also has canceled a luncheon in connection with the meeting in order to avoid any display of sociability with Gromyko.

In justifying the contradiction between Reagan's harsh words and his limited deeds, a senior State Department official told reporters at the White House briefing that the way to change Soviet behavior is to do the things that the administration already is doing in its military buildup and diplomatic activity.

"The shootdown does not change our estimate or approach to the Soviet Union. Rather it confirms it," said the official, who cannot be identified under the terms of the briefing.

By refusing to entertain such measures as a renewal of the embargo on sales of U.S. grain or cancellation of recently authorized U.S. sales of non-military equipment, Reagan departed from the recent U.S. practice of announcing unilateral economic sanctions in reaction to overseas events that generate widespread public outcry.

Such sanctions had been convenient ways for presidents to show that they were "doing something," short of dangerous military action, in the face of provocative actions abroad, but they had come under increasing criticism on grounds that over time they proved ineffective against the Soviets but painful to Americans.

Reagan's policy on sanctions may be realistic and is likely to be received with relief by farmers and businessmen who might have been adversely affected, but it also leaves him vulnerable to criticism that he is "doing nothing" to back up his rhetoric.

The president's words and actions last night suggested that the greatest impact of the downing of the Korean airliner is likely to be in the realm of public opinion. The White House briefer went out of his way to charge, as Reagan implied in his description of the Soviet action, that this is a case of "the U.S.S.R. against the world."

Despite their efforts at propaganda, the Soviets rarely have been very popular among peoples not under their sway, and the outcry over the shooting down of the airliner is likely to make them even less popular, at least for a while.

It does not necessarily follow, however, that the trigger-happiness of Soviet air defense personnel will add to the popularity of confrontational or trigger-happy policies in the West. Reagan's measured actions last night seemed to recognize the crucial difference between speaking in anger and acting in anger, especially in the nuclear age.