The Communist Party that will emerge at the end of this country's period of military rule is likely to be a very different one from the organization that appears to have been thrust into the background with the declaration of martial law 11 days ago.

There are limited signs of renewed Communist activity, such as party leaders touring the countryside or giving interviews and regional organizations endorsing martial law rule. But the party's primary task during the period of martial law is reliably reported to be a purge of its own ranks so it once again becomes a tightly disciplined organization in which power flows from top to bottom. Those party members not considered reliable will be asked to leave. Even larger numbers may have quit already of their own accord.

There is no reliable information about the number of party members who have handed in their party cards in protest against the imposition of martial law. Individual accounts, however, suggest that the number is very large, particularly among workers. If this is added to those who resigned before martial law, it seems likely that the party's effective membership cannot be more than 1.5 million--against 3 million for most of the past decade.

In the meantime, there is little visible activity at the Communist Party headquarters in Warsaw, a huge, stone-faced building in the center of the city. There is none of the customary bustle of limousines coming and going. The Central Committee, constitutionally the highest party organization between party congresses, has not met since the declaration of martial law. Even the Politburo, its executive arm, is reported to have met only once.

Middle-level officials inside the party headquarters report that remarkably little is going on. Most of the Central Committee's permanent staff have left for the provinces in order to reactivate the work of local party organizations. There is a blackout on information, and the routine news briefings for employes are not being held. The decisions being taken are made by the Central Committee secretaries who oversee specific areas such as security, foreign affairs or propaganda policy.

Day-to-day decisions appear to be made by the military Council of National Salvation --nicknamed the "CROW" by almost all Poles because its initials WRON resemble the Polish word for "crow," wrona. It is said to have its headquarters in the government building near Lazienki Park and just a stone's throw from the Defense Ministry and Soviet Embassy. The area is cordoned off to motorists.

Operational decisions are taken by the deputy defense minister, Gen. Florian Siwicki, while the martial-law leader, Gen. Wojciech Jaruzelski, is reported to attend to political and strategic issues. After making his original address to the nation announcing martial law, Jaruzelski has kept in the background. Portions of his speech are quoted every day in the press in large type but he does not seem to have any desire to be the object of a personality cult.

This evidence suggests that the military takeover was carried out in order to preserve Communist Party rule in Poland--and the party is likely to reemerge as the source of political power in the country once martial law is relaxed. Practically all senior officers are Communist Party members and Jaruzelski, in addition to his positions as martial-law chief and premier, retains the post of first secretary of the party.

Reliable sources said that, during the meeting of the state council in the early morning hours of Dec. 13, which endorsed martial law, there was some discussion about suspending the party. The advocates of this course argued that this would create an impression of evenhandedness, but, apparently in deference to Jaruzelski's wishes, the party was left alone, tactically forced into the background as a vastly unpopular organization when compared to the national pride invested in the country's Army.

There are those within the party who apparently have not remained silent, however. A long-time party member, who joined in 1956 during a wave of national enthusiasm over the return to power of the nationalist Communist Wladyslaw Gomulka, explained that the experience of the past two weeks had totally disillusioned him. After seeing the Army in the streets, he went to his local party committee and submitted a letter of resignation saying, "I joined when I believed that socialism in Poland could have a human face. I am leaving convinced that it can only be maintained by tanks."

The party member said that dozens of his colleagues had also turned in their party cards.

The lack of support of martial law among rank-and-file party members was all but admitted by a party secretary, Marian Orzechowki, in an interview with the Army daily, Zolinierz Wolnosci (A Soldier of Freedom).

Asked about the party's role under martial law, he replied: "Unfortunately, we cannot ignore the fact that only a smaller part of party members are standing the test. So far martial law has neither revived the party as a whole nor affected an essential, deep and lasting change in it and in the attitudes and activities of its members."

Orzechowki said that internal party democracy was necessarily limited during the period of martial law--but would be revived once it was lifted. This assurance is unlikely to satisfy a majority of party members who, after believing for 16 months that the Polish party was reformable, are now sinking back into apathy and cynicism following the declaration of martial law.

The official media made much out of the formation of volunteer groups of party activists assisting in maintaining law and order in the streets. The volunteers wore armbands in the national colors, red and white, and helped check identity papers, direct traffic and man roadblocks. According to the official version, the groups formed "spontaneously" from party members eager to be of service to the community.

In fact, according to unofficial accounts, the groups seem to be composed largely of retired police officers and petty clerks who have committed some minor crime in the past and are amenable to blackmail. Despite the propaganda fanfare, their role is limited--and strictly subordinate to the Army and police.

In the end, the reaction of loyalist party members may boil down to a matter of biological survival. As a Warsaw journalist remarked, "These people were scared--scared of being annihilated by Solidarity in the event of a civil war. In the event of a Soviet invasion, they were scared of being killed by the Russians as traitors, so they felt their only option was to strike first."

His observations suggest that the danger of this course of action is that the next time there is a national uprising in Poland, the workers will have less incentive to remain patient and disciplined. A peaceful solution will be much more difficult.

"Next time we won't wait. We'll eliminate the party members immediately," vowed a disillusioned Solidarity activist.