According to the formulas of effective population size,which were brought forward by Doyle and Talbot,we estimated the effective population size(N_e)for rapid growth line fundamental stock in Portunus trituberculatus.The real N_e was 213,which corresponded to a rate of inbreeding(F)of 0.23%.Results indicated that F is relatively small,and inbreeding depression was in a low level,however,the cost of conservation was too high,it did not meet the conservation requirements.In light of breed conservation model in livestock and poultry,we investigated rapid growth line fundamental stock in P.trituberculatus on methods of selecting parents and ratio of dams and sires and the size of conservation population.We made the rules as follows:random selecting parents,the ratio of dams and sires is 1∶1,and the number of dams and sires is 131,respectively.In this situation,genetic diversity of rapid growth line fundamental stock is preferably rich,which satisfies selective breeding,at the same time the cost of breed conservation is economical.This is only a theoretical model of breed conservation,and it needs the process of gradual improvement of breeding populations in the future.