Abstract: This paper embodies preliminary biological research of Lipotes vexillifer, including body color, age, growth, diet, and reproduction behavior, Specimens were caught from the middle reaches of the Changjiang River in 1979 and thereafter.The body color of Lipotes is rather simple, being light gray dorasally and white ventrally. However, there are conspicuous decorative marks on its neck and tail. Teeth of Lipotes have been used for the determination of the age. Based on the outline and the pulp of the teeth, youngs, adults and old individuals are distinguishable. The relationship between age and body-length are as follows:Y♀=X/0.003394X+0.008251±13.6476 Y♂=X/0.00453X+0.004715±14.8498 (X-age,Y-body leugth in cm) In general, females are larger than males of the same age, and, statistically, six morphological parameters are significantly different between both sexes. To describe the relations among various bodily indices, the formula W=aLb1Sb2（W, L and S denote weight, length and girth, respectively） is more authentic, and W=0.003418 L1.2681 S（1.1949） is available to calculate the weight of an animal during field survey or whenever the animal is unable to be weighed.The mature age of male dolphines is over 4 years, of females is 6 years. Copulation probably takes place from April to May. Lipotes feed on freshwater fish and live in groups. Their preference for certain water velocity is obvious. Their cruising speed is 7.5—9.7 km/hr. when following the water current, 2.7—4.9 km/hr. when again st the current.Lipotes is mild in nature, causing no harm to other aquatic mammals and human being. In the Changjiang River, they were found to live with Neophocaena in same habitat.