Abstract: In the paper, the rice seeds under various physiological states-dry, wet reveal bud and bud off were irradiated with 60Co-r ray, and the mutagenic effects were detected. The results showed that the radiation sensitivity varied with the physiological states of rice seeds. Most sensitive state was reveal bud of seed, followed bud off, wet and dry state. The mutagen doses of LD50 for reveal bud and bud off state hold 15-17% of that dry seed state needed.In M2 generation, the mutation frequency of chlorophyll deficient, heading date, plant height and sterility were observed. The results show that the mutation frequency of germinating seeds were higher than the dry seeds. The mean mutation frequency might raise 68.5% for reveal bud state and might raise 54.1% for bud off. The optimal radiation dosage for reveal bud and bud off states ranges 8-10Krad all.