Abstract: We obtained 77 sequences of 5-flanking regions of GHSR genes from two populations (fast-growth group and normal-growth group) of Nile tilapia (Oreochromis niloticus) by PCR amplification and sequencing method, and detected 57 variation sites (12 inserting or deleting sites and 45 polymorphic sites) and 16 kinds of haplotypes. Hap2 might be the original haplotype. There were two branches (A and B) in the phylogenetic tree of 16 kinds of haplotypes. Branch A contained 11 kinds of haplotypes which could be found in both groups but showed higher-frequency distribution in fast-growth group; while Branch B containedfivekinds of haplotypes which only distributed in normal-growth group. The nucleotide diversity (Pi), haplotype diversity (Hd) and average number of nucleotide differences (K) in fast-growth group were higher than those in normal-growth group. The Fst value (-0.200 0, P0.1) and genetic difference (120%, mainly from intragroup) between the two groups suggest that no genetic differentiation exist between the two groups.