Abstract: Fifty-one sequences of the hetR gene from Nostoc and related species of cyanobacteria were studied. The coding proteins of hetR were analyzed by bioinformatics and phylogenetic analysis. The adaptive evolutionary characteristics of hetR were studied using the branch, site, and branch-site models. Phylogenetic analysis showed that the inner group could be divided into four large branches. Based on the adaptive evolutionary analysis, no significant positive selection sites were detected in other branches and algae strains of the three evolutionary models, indicating that most of the sites were under negative selection pressure. However, significant positively selected sites (126T) were detected in Nostoc commune (CHAB2802), indicating that the hetR gene has undergone adaptive evolution in Nostoc.