We have 189 specimens available for this work. One-hundred and sixty-seven specimens from the Yangtze, Yellow Sea and South China Sea populations were aged and used in studying the growth pattern. A modified power model was employed in tilting the growth curves of the Yangtze and the Yellow Sea populations. The Laird’s model was used for the South China Sea population. Testis weight for 75 specimens were available for demonstrating the development of the testis. An adapted S-shaped growth model was used in fitting the testis weight/age curve for the Yangtze and the South China Sea populations. Data from 82 females were available for estimation of reproductive parameters. Sexual maturity was determined by anatomical and histological methods. The results indicate: (1) The growth rate of the body length was pronouncedly higher in the first 4 GLGs of life and ceased to grow at the age of about 8 in the South China Sea population while the Yellow Sea and the Yangtze populations grew relatively slower in the first few GLGs of age, and kept growing in all the ages examined, but the females of the Yangtze population seemed to grow slower than the males after 6. (2) The testis developed earlier and faster in the South China Sea population. (3) The minimum age of the sexually mature finless porpoise is 4 GLGs for males and 5 GLGs for females in the South China Sea population. The minimum age at sexual maturity was about 5 GLGs in both the males and females of the Yellow Sea population. and about 6 in those of the Yangtze population. The age at attainment of sexual maturity varied with individuals. The maximum immature were 8 and 10 GLGs in the males and females of the Yellow Sea population respectively. 7 in the females of the Yangtze River population. (4) The porpoise in the South China Sea population gave birth in June through March with a peak in August through December while that of the Yangtze and the Yellow Sea populations mainly gave birth in April and May. The differences among the three populations in growth and reproduction may be attributed to their different habitats. The higher surface temperature in the tropical water may have enhanced both the rapid growth and the sexual and physical maturity of the South China Sea population.