In the autumn harvest season of Bohai Sea and northern Yellow Sea,the Chinese prawn (Penaeus orientalis) was traditionally caught by using varioustrawlnets. In order to protect environmental conditions of fishing ground and tosave the juvenile fishery potentiality, in 1983-1985 the behaviour of penaeidprawn was observed and trial fishing by drift net was taken as well. From thepractice a certain amount of blocked prawn dropped from the drift-net webbingoccurred. By analysing, the technical precautions against the dropping were sug-gested: 1. The each main webbing of per drift net should be used traverse. The hori-zontal hanging coefficient (u_1) should increase from 0.67 to 0.71. And the meshsize (2a) may be more than 62 mm. 2. Through diving observations, no such dropping was found during the haulfrom bottom to the surface. In the haul time, the hauling speed of float line, leadline and webbing of net should be equal, meanwhile to keep the side of net web-bing against current upwards. 3. During the haul, it is necessary for using the floating prawn pocket to de-crease the dropping blocked prawn.