The purpose of this study is to investigate the relationship between cell transformation and hprt gene mutation induced by α irradiation in vitro. The results showed that the colony formation efficiency (CFE) of human embryo lung cells in soft agar increased after irradiation with 0.25—5Gy, which meant inducible cell transformation by α irradiation. Mutation frequency of hprt gene was found increased with the increase of the doses of α irradiation. Further analysis indicated the positive linear correlation between CFE and the variation coefficient of hprt gene. So,the carcinogenesis induced by α particles maybe is relative to hprt gene mutation.