Based on the specimens of foetuses and testes collected from the Changjiang River since 1978, some characteristics about the embryonic development and the histological structures of testis in Neophocaena phocaenoides were studied preliminarily. Morphogenesis in the foetuses of Neophocaena phocaenoides distinctly displayed the evolutive process in cetacean from terrestrial animal to aquatic animal. Statistical results of 18 foetuses indicat that: the relationship between foetal weight and length is represented by W=0.0305L~(2.7983), the growth rate of foetus is about 9.1cm/month (0.303cm/day), mating takes place from May to August, the gestation period is about 9.4 months, parturition time is from march to April per year. The relationships between testis weight and body length are as follows: Y=-2.4092 + 0.1189X (foetus) Y=0.0170e~(0.0606X) (postnatal) Testes enlarge significantly when males attain 140cm of body length. Histological examination indicated that senescent testes were characterized by shrunk seminiferous tubule, fibrotic tissue and thicker tunica albuginea. Male propoises are reproductive senescence at about 169cm or 14 years old. In addition, the ultrastructure of sperm of Neophocaena phocaenoides is discribed. The population status of Neophocaena phocaenoides in the Changjiang River was discussed chiefly from the angles of reproductive biology.