Abstract: The ultrastructure of follicular cells in the Exopalaemon modestus ovary,and their connection with oocytes at the different developmental stages were observed with a transmission electron microscopy.Developed with the oocytes,follicular cells experienced a process from development to deterioration.At the stage of yolk mass-occurrences,oocytes were surrounded by several layers of follicular cells,and sinuses extended between the layers.Endoplasmic reticulum,Golgi bodies,mitochondria,ribosomes and pro-yolk granules were abundant in follicular cells.At the autumn of eggs,follicular cells started to retrogress sequentially from the inner layer to the outer layer,sinuses atrophied.These morphological changes are in keeping with the observation that follicular cells function in absorbing nutrients from blood,synthesizing and transferring pro-yolk substance to oocytes.The function is somewhat different from those documented for Scylla serrata,Penaeus penicillatus and Eriocheir sinensis.