This paper describes the morphology,structure and content of the spermathecae in Portunus trituberculatus and the its corresponding relationship with ovary by analyzing samples collected during 2005-2006 in East China Sea.In pre-copulation period,the wall of the spermathecae was thin,but the lumen had been partitioned into two chambers,dorsal and ventral(Apr-Jun);Then the spermathecae began to shrink and the wall became relatively coarse while the mucosa developed secretory stratum(Jul-Sep);Finally,the wall evidently proliferated,while its polynuclear columnar epithelium degraded completely.There was nothing but one jelly-like matrix existed in the lumen as revealed by the H-E staining.In copulation period(Oct-Nov),the lumen extended significantly due to the fact that spermathecae received much male material and thus the wall became thin.Moreover,the dorsal part developed many protuberances that much like the Chinese character "凸" or "丁".Correspondingly,the ventral part also developed a few folds.Sperm plug,consisting of four matrixes: MM,FM,APSP,TPSP,formed in the mating process by the reactions between the male matrix and female secretion.This was an important character which implied the crab had successfully experienced mating activity.The spermatophores only existed in the superficial part of the male matrix on the top of dorsal chamber.However,the sperm plug disappeared within no more than two months,which was not responsible for protecting and nourishing the sperm.The dorsal protuberance controlled the whole spermathecal volume,whose formation and degeneration had close relationship with the transportation of spermatophores.In post-copulation period(Dec-Mar),the spermathecae shrinked completely.The dehiscent spermatophores firstly aggregated in the intersection of the dorsal and ventral parts and then stored in the ventral chamber of the spermathecae for the successive fertilization.The relationship between spermathecae and ovary was close and therefore might even have some evolutional significance.Combined with the developmental phases of spermathecae and ovary,we could better differentiate and understand the dynamics of the resource of P.trituberculatus.