The finless porpoise, Neophocaena phocaenoides, is distributed in the form of a narrow band along the coast line of tropical and temperate Asia and in the Yangtze river.The differences of external measurements among the populations in Chinese waters were studied using t-test, analysis of covariance and discriminant analysis. Based on 226 specimens collected between 1974 and 1993 by the Cetacean Research Laboratory, Nanjing Normal University. A total of 84 from Yangtze population, 97 from Yellow Sea population and 45 from South China Sea population was available for study. According to the distinct differences in external measurements, skull measurements (Gao,1991), growth and reproduction pattern (Gao et al,1993) among the Yangtze River, Yellow Sea and South China Sea populations as well as the differences among the Chinese populations and the South Asian and Japanese populations, the authors suggest that Neophocaena phocaenoides be consisted of 3 subspecies: 1) Neophocaena phocaenoides phocaenoides (Cuvier,1829 ), inhabits the coastal waters of South China Sea and southern part of East China Sea. Diagnosis: Dorsal ridge originates after the midlength on dorsum,10-14 rows of tubercles, tubercle area is 48-120 mm or larger in width. 2) N. p. sunameri (Pilleri and Gihr, 1975), inhabits the coastal waters of Yellow Sea, Bohai Sea, East China Sea and off the west coast of Korea. Diagnosis: Dorsal ridge originates before or at midlength on dorsum,16 mm or more in height, and reaches 55mm in maximum, 2-9rows of tubercles, may exceed 9 rows in Japanese porpoise, Tubercle area 12 mm or less in width, may exceed 12 mm a bit in Japanese porpoise. 3) N.p. asiaeorientalis (Pilleri and Gihr, 1972), inhabits the middle and lower reaches of the Yangtze River, the Dongting Lake and the Boyang Lake. Diagnosis: Dorsal ridge originates before or at midlength on dorsum, 2-5 rows of tubercles, tubercle area 8 mm or less in width. Dorsal ridge hardly exceeds 15 mm in height. This is the only subspecies inhabiting freshwater. Statistical analysis also demonstrates that: among the three populations in the Chinese waters, individuals from the Yellow Sea population have the longest snout, while those from the South China Sea have the shortest; Individuals from the Yangtze population have the thickest blubber, while those from the South China Sea have the thinnest; The girth of the individuals from the Yangtze population is relatively larger than that from the other two populations.The barrier between N. p. phocaenoides and N. p. sunameri may be attributed mainly to the water temperature in different areas. That between N. p. asiaeorientalis and the coastal population may be mainly attributed to the salinity of the river and sea waters.