We aimed to identify polymorphisms in the coding regions of the Salmo trutta caspius (s. t. caspius) growth hormone gene for comparison of the rate homology between sequences cited regards salmonids, because the variation between sequences of exons is very important at finally can change in the rate of expression of gene growth hormone, however this gene identified by marker genetics in salmonids, and in those of Salmo salar (s. salar) and salmo trutta (s. trutta). This single copy nuclear gene contains six exons, that the length of the exon fragments almost 1900 base pairs between nucleotide 35 and 1907. In s. t. caspius. Selective PCR reaction, and sequenced the products, that including fragments of from first to end of the GH gene. We also describe a novel polymorphism of the six exons fragment, these fragments indicated for studies regards evolution of fish GHgenes, phylogeny of fishes, and genetic selection. The segments of GH exon were analyzed by DNAMAN program genetics. The results are shown, there were almost 90%, homology between the first three exons of S. t. caspius and S. salar accession number (AY614002.1) Regards other Salmons; S. salar (Accession number, M21573.1) and Rainbow trout there weren't any homology, exon fragments second, third, fourth, fifth and sixth, the homology were high (almost 90-95 %), however between fragments of salmons, the rate of homology were high but the length of fragments between salmons were different. The length of fragments in s. salar more than other salmons including R. trout and S. t. caspius.