Mud clam (AustIiella corrugata Deshayes, 1843) is marine species which now has high economic value, however because of being over catching and has no seed production, the yield of mud: clam is being depleted. The article presents the research result in some reproduction biological of mud clam in Quang Ninh province in Vietnam. The inital result shows that the gonadal development of mud clam undergone in 5 stages. The distinction between male and female depends on observing gonadal in reproductive season. The reproductive season of mud clam begins from April to October and becomes highest in June and July. Sex ration is 1:1 and first maturity size is 30 mm. In the group size 30-50 mm, the reproductive capacity of mud clam is from 676,800 to 1,525,000 eggs/female. This research result is an important base to construct the process of mud clam seed production.