Abstract:The mature panicles of rice were treated with 60Coγ-rays in the range of 0～0. 372 kGy.The male sterile line used as the female plants were fertilized with γ-irradiated pollen manu-ally.The dose effect of the irradiated pollen on double fertilization was investigated.It wasfound that double fertilization of the irradiated pollen was suppressed to different degrees ascompared with the control. The effect was noticeable as that the fuslon time of the male nu-cleolus with the female one was delayed with the increasing of γ-radiation dose.The delayedtime was less than 13 hours when the dose was below 0.186 kGy and it was more than 15hours when the dose was above 0.279 kGy.Furthermore, several types of deformed embry-onic cells and endosperm nuclei were observed.