A study on the feeding habit and food basis of hairtail fish (Trichiurus lepturusLinn.) as well as the relationship between its food organism and fishing grounds hadbeen carried out during the years from 1960 to 1981. Food organisms and stomachcontent samples were collected from some fishing grounds along the coastal waters ofZhejiang Province and off the Chang Jiang estuary during 1963--1965.The results are as follows:1. Hairtail fish is omnivorous mainly feeding on planktonic crustaceans (Eupha-usiacea etc.) and also fishes, Cephalopods, Chaetognaths etc.2. The Euphausiacea resource of the Dong Hai region is very abundant. Thequantitative distribution of the shrimp seems verey closely related to the migration ofhairtail.It obviously manifests in some fishing grounds along the southern coastal waterof Zhejiang province in winter and spring seasons and also occurs at the mouth ofChang Jiang in summer and autumn.3. The present paper deals with the analyse of the structure of plankton com-munities in some fishing grounds and the discussion of the relationship with the move-ment and migration of hairtail fish.