The group behavior of the black finless porpoise was listed in thispaper. Three groups of the finless porpoise were captured and surrounded in thedifferent water area using the special net in the middle and lower reaches of theYangtze River in 1984, 1989 and 1992. Based on the records of observation for 42days and nights, this paper has made an overall descriptions and comprehensiveanalysis of its untamed behaviors of schooling, mother--calf, feeding, court-ship, playing, escaping, resting and being "altruistic", etc., upon its breath onthe surface of water. This observation not only will help to protect and breed theporpoise but also can apply to protect in the natural protection section and to breed.