Objective To analyze the data from Online Mendelian Inheritance in Man (OMIM) to understand more about it, and provide reference to researchers using this database.Methods 19414 mutations which have definite relevant phenotypes from OMIM were obtained, then these mutations with three databases (1000 Genome Project,GO-ESP,ExAC) which record the mutation frequency in different population were compared.Results Most of the phenotype-related mutations from OMIM are rare mutations whose mutation frequency is less than 1%:18866 in 1000 Genome Project, 18981 in GO-ESP, 18979 in ExAC.The number of mutation whose frequency is more than 1% is 548433435 in 1000 Genome Project, GO-ESP, ExAC, respectively.And there are 320 mutations whose frequency is more than 1% in all databases.In all phenotypes, there are 127 polymorphism phenotypes, 584 susceptibility phenotypes, while in 320 ( 1.6%) phenotypes with common mutations, there are 62 polymorphism phenotypes, 88 susceptibility phenotypes and occupies 48.8%, 15.1%, respectively.Conclusion Approximately 97.5% mutations in OMIM are rare mutations.Polymorphism and susceptibility enrich in common mutations, especially in the mutation whose frequency is more than 10%.