GH gene of GIFT (genetically improved farmed tilapia) was isolated from blood DNA by homology-based cloning. GH gene included five introns and an open reading frame of 615 bp which encoded 204 amino acid residues. A site in exon 6 of GH gene showed SNPs (A/G) through random sequencing. PCR–RFLP method was used to detect SNPs in GIFT population and the correlation between weight gain and SNPs was analyzed. The results showed that the weight gain of female individuals with GG and GA genotypes was higher than that of which with AA genotype, but there was no significant difference. The weight gain of male individuals with AA genotype was significantly higher than that of which with the GG genotype (P<0.05).