Because the current common use crab pots(pot diameter 60 cm,height 25 cm,mesh size of clothing net 2a=32 mm)are causing the serious damages on the juvenile crab resources of Portunus trituberculatu in the East China Sea,a selective crab pot with escape gap opened on the framework for juvenile crab was designed.The productive tests in 32°30′-33°00′ N,124°00′-124°30′ E were carried out during Nov.2009.The results showed that the proper height of the escape gap is almost the same as the largest shell height of P.trituberculatu.If the minimum criterion of catchable body weight was 125 g,the height of selective escape gap was 33 mm which can be estimated from the relationship between shell height and body weight; The selection curve of the escape gap can be described by piecewise function without 50% selective shell height,which is different from “Logistic selection curve” that is usually used to describe the mesh selection curve of trawls,shrimp trawl,stow net and eel pot with 50% selective length.The selective rate in number can be denoted by the average selection rate of shell height groups,by ChiSquare(χ²)test,while its values of productive tests were smaller than 20%,it presents higher release rate; however,it shows almost no effects caused by the size of gap for escaping,on the survival of juvenile crab were observed.At the same time,we suggest the minimum size of catchable criterion could be referenced for the formulation of the fishery regulation.