The present study represents a preliminary analysis of the cytochrome b protein sequences in the salmo trutta fario, salmo trutta caspius, salmo trutta trutta and salmo salar has been determined. The cytochrome b gene consisting 1141base pairs that encoding 380 amino acids and has been five origins ORF sites from nucleotides number of 125 to 718 which placed number of 72, 40, 37, 67, 32, respectively from first to end of gene. The amino acids sequences were compared with those of other salmonids such as salmo salar, salmo trutta and salmo trutta caspius, in this regards, the sequences aligned by DNAMAN program computer, results are shown regards salmo salar, salmo trutta trutta has 380 amino acids and same homology almost 99% but regards salmo truttta caspius, has 78% homology. There were more variation from 20 first amino acids than other parts of segments, however there is not full length of cytochrome b gene in samlo trutta caspius. The sequence features of the 3RD structure protein accessed and compared between species of salmonids, The results are shown there are same homology between structures of protein.