[en] Dry seeds of maize inbred lines LY8405 and PH6WC were irradiated by fast neutron at doses of 0.36∼4.19 Gy to explore the cytological effect of irradiation on maize for germplasm innovation and improvement. The results showed that with the increase of absorbed doses, the mitotic index of root tip cells decreased, while the rate of nuclear aberration increased. The chromosome division behavior of irradiated inbred lines LY8405 in M1 generation was the most obvious at dose of 4.19 Gy, followed by the irradiated inbred lines PH6WC at dose of 2.48 Gy. Abundant mutation types appeared in M2 and M3 generation of inbred lines LY8405 and PH6WC under fast neutron irradiation, including those of plant shape, leaf color, panicle length, plant height, grain shape, and grain size, etc. Biological and cytological studies show that with maize seed irradiated by fast neutron at 0.36∼4.19 Gy, the appropriate dose range for breeding is 2.48∼4.19 Gy. (authors)