The optimal temperature for each bacterium differs, which is related to its gene sequence. In order to explore the correlation between them, the known genome sequences of 92 bacteria with own different optimal temperatures were selected as the study material, then the common homologous protein from 92 bacteria were searched, and frequencies of the amino acids in homologous protein were calculated. A significant correlation between the frequency of the amino acid in homologous protein and the optimal growth temperature was realized. The analysis of the sites in homologous genes showed that the helix regions in the protein sequence were the most correlated with its optimal growth temperature. This study presents important significance on understanding the mechanism of the bacterial adaption to the temperature as well as designing the mutation to improve the protein stability.