The objective of this study is to produce genetically male Nile tilapia (Oreochromis niloticus). Ten suspected sex-reversed YY female Nile tilapia was paired with normal XY male Nile tilapia, respectively, to breed. Progeny test was carried on to 8 groups with fry. Results showed that no sex-reversal YY female was discovered among the 8 groups. In addition, the effect of photoperiod on growth rate and feed utilization efficiency of Nile tilapia (O. niloticus) was investigated. The fish were exposed to four photoperiod (light: dark, L:D) cycle (24L:0D, 18L:6D, 12L:12D and 6L:18D). The fish were feed a tilapia diet at a daily rate of 5-4% BW, two times a day for 90 days. The best specific growth rat and feed efficiency were achieves at 18L:6D.