Abstract: Six doses 0Gy, 10Gy, 50Gy, 100Gy, 150Gy and 200Gy were used to study the effects of seed irradiation with 60Coγray on the growth of seedling of Godetia grandiflora Lindl.in vitro in this experiment. The results showed that the number of roots and leaves, and plant height all decreased with the increase of irradiating doses (50-200Gy). Moreover, the higher dose, the higher death rate, and the Half Lethal Dosage (LD50) for the seedlings of 41 days was 150 Gy. Mutants were found amongst seedlings in all treatments 70 days after culturing, including flower colour, shape and the structure of patals. This indicats that gamma ray irradiation can increase the frequency of mutations and produces special types of flower in Godetia grandiflora breeding.