The Chinese mitten crab Eriocheir sinensis is a commercial important species in China. The aim of the study is on the individual male reproductive potentiality under the laboratory-reared conditions by evaluating the rationality of the parental sex ratio (♀:♂=2-3:1) during the process of breeding. The results showed that male has the capacity to complete three successive mating activities; prior to losing mating ability, male has contributed more than 60% semen material including the sperm number of ≥6×10⁹ contained in vasa deferentia; male multiple mating activities have no obvious effect on females' fecundities; after egg-carrying, female spermathecal weights displayed no distinct deviations either in the laboratory or field-reared conditions, while both spermathecae still contained certain semen material, which means that male would have provided enough sperm to satisfy females' fertilization. Therefore, this parental sex ratio should be proper and practical. Moreover, male big size and reproductive strategy should be two important factors to avoid occurrence of sperm limitation, which make the potential ratio of sperm to egg up to (1.59-10.86)×10³:1. Besides, our study reveals that this sex ratio adopted extensively in process of seed breeding, can be further optimized and elevated to 4:1.