Abstract: At the early development of the embryo, short bristles were observed on eachside of upper jaw in Neophocaena phocacnoides.The number of the bristles variedfrom 1-3 on the left and 2-3 on the right.Semicircle ear outline was visible. The penis of male foetus was exposed out of body.The swimming organs(flipper,fluke and midway anus to luke notch)developed prominently. As embryo develo-ped,external ear outline of foetus disappeared and the penis of male foetus concea-led in the penial pouch. These morphological changes in the course of the embryo-development indicated that cetacean ancestor might have lived on land and that ce-tacean adapted to water environment whcn coming into water secondly.In addition,statistical analysis on 17 foetuses and juveniles showed that: the growth rate offoetus was 9.08cm/month(0.303cm/day)in Neophocaena phocacnoides, the gesta-tion period may be about 9.4 months in Neophocaena phocaenoides in the YangtzeRiver,and mating may take place from June to August,parturition time fromMarch to Mav each Vear.