State Department officials have been studying the feasibility of admitting thousands of Palestinian refugees from Lebanon to the United States. But the department last night denied earlier reports that Secretary of State George P. Shultz had ordered the study and said the idea had been abandoned as impractical.

State Department spokesman John Hughes, contradicting what several officials said on background earlier in the day, contended that Shultz had given no such order. Instead, Hughes said, a study of that nature had been initiated without Shultz's knowledge at "a low level," but he insisted that "it had no standing" and was not being pursued.

Earlier, several officials in various State Department offices, speaking on condition they not be identified, confirmed as "substantially accurate" a report by a Washington newsletter, the Middle East Policy Survey, that Shultz had instructed the bureau of Middle East affairs to undertake the study.

Some also provided details not included in the newsletter report. They said that the study envisioned the possibility of admitting as many as 10,000 Palestinians and said that it was being pursued despite warnings from some State officials that the idea was likely to encounter heavy opposition from the American public and Congress.

In addition, the Middle East affairs bureau issued a statement yesterday afternoon acknowledging that "we are looking at the possibility of a refugee admissions program for certain Palestinians in Lebanon."

After Hughes disassociated Shultz from the study, some of the officials who described the study earlier were contacted again last night by The Washington Post. At that time, they said there had been "some confusion and misunderstanding" earlier and added that they were unable to say more.

The earlier accounts provided by the newsletter and by department sources said that Shultz had called for the study partly out of humanitarian concern for the refugees and partly because the Israeli and Lebanese governments believe that resettling some of the estimated 800,000 Palestinians in Lebanon would ease tensions in that country.

The sources said the study initially proposed admitting up to 50,000 Palestinians but that the number was scaled back to a theoretical maximum of 10,000 after some department officials expressed concern about public perceptions of the Palestinians being associated with Middle East terrorism.

Other objections cited by the sources were that such a plan would encourage the Arab world to continue ignoring its responsibilities to the Palestinians, disrupt immigration policy by favoring the Palestinians over other groups and cause resentment at a time of high domestic unemployment.

In addition, the sources noted, the idea is at odds with the Reagan administration's argument that its struggle against communism in Central America is, in part, an attempt to ward off the possibility of having to absorb thousands of refugees from that area.

Some sources said part of the impetus for the study came from Shultz's recent discussions here with Israeli Defense Minister Moshe Arens, an advocate of resettling the Palestinians from Lebanon.

Hughes acknowledged that Shultz had discussed the refugees with Arens, but he insisted that the secretary had done so only in the context of expressing concern about their plight and had said nothing about the United States taking in Palestinian refugees.

The sources also said the study was being directed by David T. Schneider, a deputy assistant secretary for Mideast affairs. Last night, however, these sources said they no longer were certain that Schneider had been involved, and Hughes said that Schneider's connection had "been peripheral at best."