Abstract: Eggs of female Oreochromis niloticus and sperms of male Sarotherodon melanotheron were collected by abdominal squeezing of the broodstocks. The egg shape, size, color and accumulation of yolk granules at different matured stages were analyzed by optical microscope and dissecting microscope techniques, the result showed that the immatured eggs were oval-shaped and covered with small blood vessel; the matured eggs were pear-shaped, eggs diameter were 0.5~ 1.6 mm, they were coated with a transparent egg membrane and filled with large amounts of golden yellow yolk granules; the over-matured eggs had irregular shape, with some liquefied yolk granules. The sperms were observed by scanning electron microscopy technique, normal sperms were composed with head, middle and tail piece, the head was a elongated cone, long diameter was 1.82(0.35)m, wide diameter was 1.41(0.34)m; the middle film was short and cylindrical, long diameter was 0.74(0.08)m, wide diameter was 0.16(0.06)m; the tail, single flagellum structured, was extremely long, was 16.42(0.35)m. Three types of abnormal sperm including short-tailed, double headed and two-tailed, were also observed. The results could provide some basic dates to improve tilapia artificial hybridization techniques.