Abstract: This paper deals with the breeding population biological characte-ristics of Leucisus brandti which is the only species of Cyprinidae during upstreammigration in Suifen River. 1793 samples were measured in 1989. The breeding po-pulation structure of L. brandti was as follows: (1) The population was consisted of 2--5 years old individuals, in which 3years old was 64.6%. The average body length of the fish was 293(225--425) mmand its average body weight was 450(175--1600)g. (2) The sex proportion was 1: 1.63.The fecundity was 34, 232 (15,222--88,660)eggs and the average diameter of eggs was 2.0(1.7--2.2)mm. The migrating sea-son was in May to June and spawning period was in middle May to early June. (3) The population was 30,000 individuals or so in 1989. Up to now,the popu-lation has greatly decreased. The ecological environment of spawning populationand spawning area should be protected. A Iarge scale artificial releasing of L.brandti should be adopted.