Abstract: This paper describes the structure of testis and spermatozoon in the Chinese freshwater catfish, Leiocassis longirostris. The testes are branched into finger-like structures. The posterior portion of the testis is purple and is composed of simple columnar epithelium. This purple portion does not produce or contain spermatozoa. The testis has a lobular type of organization and consists of somatic and germinal cells. The somatic cells in the testis include fibroblasts, boundary cells, Sertoli ceils and Leydig cells. The lobule is composed of cysts and the germinal and Sertoli cells in the cysts. The Leydig cells are located between the lobules. The germinal cells include spermatogonia, spermatocytes, spermatids and spermatozoa. The gamete consists of a head, a mid-piece and a tail. The head is short, round or oval in shape, containing a nucleus but no acrosome. The nuclear fossa is very developed. The tail is very long, containing lateral fins. The spermatozoa have rich saceiform structure and mitochondria in the base of flagellar.