The base-Iine data of the tagging-and-recapture prawns, the statistics from fishing grounds, the relative amounts of catching young prawns caperimentally in the three hays of the Eohai Sea ( Eohai, Laizhou and Liaodoxzg ) and hydrologic investigation in Iarge areas were used to analyze the pexzaeus prawn's regular migration and distribution in the three bays and other fishing gxoungs as well as the forming of the central fishing grounds. The results are as follows: 1.According to the data of the tagging-and-recapture prawns in the autumn fishing, the prawns migratory speed and recapture rate in each Iife is ascertained. 2， According to the annual change of the prawn shoal density in the distributive maps charted by the telegraphic records in the autumn fishing, it seemed that the prawn fishing grounds Iosely related to the cold water masses in September, and to deeper and relatively high temperature areas in Octoher. 3.Early in Autumn to the end. of September of the young prawns in the three hays and the Laihe Estuarine migrated from the shallow waters of low salinity and high temperature (salinity 22-28‰ and bottom temperature 2fi-28℃) to the central-eastern Bohai Sea and central Liaodong Bay of high salinity and. low temperatore(salinity 34-31‰ and. bottom temperature 20-23℃), It revealed that the site and stability of the central fishing ground and the density of the prawn shoals had a close relation to the distributive form of the isotherm (longitude or latitude) with botom temperature 20℃ and. bottom salinity 30.5‰. 4. The investigation data of the relative amounts of the young prawns in the bays during the past fifteen years showed that the prawn abundance in the Laizhou Bay and the Bohai Eay kept a higher level from 1972 to 1981, except 1976. That could be regarded as the basis of forming the fishing grounds in,th.e sea of Yantai-Weihai from the Iast ten days of August to the first and second ten days of September，and in the Liaodong Bay from the last ten days of September to the first ten days of October.