Abstract: In this paper, the seeds of Coix lacryma-jobi varieties CDT and Y 159 were treated with different doses of ⁶⁰Co-γ and ethyl methylsulfone（EMS） at different concentrations respectively, and the effects of ⁶⁰Co-γ irradiation and EMS on seed germination, seedling mutation rate and plant height were analyzed, which aimed to screen the optimal irradiation dose(⁶⁰Co-γ) and concentration（EMS） for inducing mutation of C. lacryma-jobi. The results showed that ⁶⁰Co-γ irradiation dose and EMS concentration had significant effects on seed germination rate, seedling mutation rate and plant height. With the increase of ⁶⁰Co-γ irradiation dose and EMS concentration, the seed germination time was delayed, the germination rate was decreased and the seedling was shorter, while the seedling mutation rate was gradually increased. Additionally, half lethal doses for CDT and Y 159 were 406.305 Gy and 284.795 Gy under ⁶⁰Co-γ irradiation respectively, while half lethal doses for Y 159 was 2.453% under EMS treatment.