Abstract: In view of the problems that the low success rate of artificial larval breeding and the lack of researches about early development of Paphia undulata，scanning electron microscopy was used to observe and describe the embryonic and larval development process of the clam，and the clear SEM photos showed the morphological changes of the early development were obtained. In Paphia undulata,the diameter of ovum wass 58.49μm, the shell length of D larvae and attached larvae wer 87.38μm and 200-220μm respectively.The morphological size was smaller than bivalve mollusk,such as Ruditapes philippinarum,Sinonovacula constricta,Mercenaria mercenaria,and so on.