The present paper deals with seasonal variation of ovary weight, number of eggs spawned and carapace width (CW) of Orithyia sinica (Calappidae, Brachyura) based on the samples monthly collected from May to November 1981. Ovary weight of the prematured crabs (CW, 50 mm) was less than 0.5g. Biological minimum size of the female was approximately 55 mm in carapace width. Ovary weight was 0.01-0.5g in the premature stage, 3.0-15.9g in the virgin stage, and 0.2-1.5g in the ovigerous stage. Number of eggs spawned depended on the size of the females, and it ranged from $240{ imes}10^2;to;1073{ imes}10^2(mean;ca.542{ imes}10^2)$. The diameter of eggs spawned was in the range of 547-913 ${mu}m(mean ca.712{mu}m).$