In the GH exon 1 region, a microsatellite locus was detected in 100 juvenile samples from a cultured stock of olive flounder, Paralichthys olivaceus. The polymorphism of this locus and the genetic effect of genotypes on economic traits in this stock were analyzed. The results indicated that this microsatellite locus was polymorphic. Five genotypes and three allele were tested. The frequency values of A, B and C alleles were 0.339, 0.609 and 0.517, respectively. The observed heterozygosity and expected heterozygosity of this locus were 0.540 3 and 0.511 2.And the polymorphism information content and the effective allele number were 0.423 8 and 2.045 8, respectively. One-way ANOVA result showed that fish with genotype AC were heavier than those with other genotypes and C was an effective allele in flounder weight.