Abstract: Sperm nuclei have the ability of swelling and forming male pronuclei immediately after fertilization in eggs of bisexual reproductive fish. By contrast, the fertilized eggs of gynogenetic crucian carp (Carassius auratus gibelio) suppressed the appearance of male pronuclei. Using the method of demenbraned sperm injection together with cytological and ultrastructural observation, we made a preliminary examination on the biochemical charateristics in sperm nucleus development at early fertilization of two kinds of fish eggs, and focused mainly on the egg of gynogenetic crucian carp which regulated the unique reproduction via fertilization. The result that in cytoplasm of bisexual eggs the presence of certain concentration of Ca2+and the reduction of disulfide bond is of necessity at the development of sperm nucleus. But in ooplasm of gynogenetic crucian carp the Ca2+and disulfide bond reduction was not directly related to the inhibition of sperm nuclear development. On the other hand, the cytoplasm in gynogenetic eggs abnormaly high activity of phosphatase. Further research showed that there are plenty of relative factors which induce the forming of pronuclei from sperm nuclei in heavy ooplasmic fraction of bisexual eggs but none or less in gynogenetic eggs. The ooplasm of gynogenetic crucian carp may also lack some high molecules responsible for membrane assembly of male pronucleus.