Approximately $3 million worth of made-in-china boys' and men's flannel and corduroy shirts has been illegally halted at the U.S. borders because of a hastily imposed quota on imports, four textile importers charged in a suit filed here yesterday.

The importers said they made arrangements to buy the shirts for the fall season here before the June 5, 1979, quota was announced, and that the shirts already are paid for.

Because of the time frame involved, the importers said in their lawsuit that the fall merchandise will have to be stored at restrictive prices or will deflate in value so much before it is seasonal again that the shirts might have to be destroyed.

The importers said the U.S. government failed to take the normal step of considering the effect of new quotas on outstanding contracts such as the one they had with Chinese manufacturers.

They said the number of shirts at issue account for 2 per cent of the total number of imports in the category involved, and that the U.S. had failed to waive the quota restriction after repeated inquiries from the importers. It is too late to obtain the equivalent number of shirts from other countries, they added.

They asked U.S. District Judge Louis F. Oberdorfer to order the shirts released and allowed through customs.