Abstract: The gene effect difference of maize variety Mo17 which is an important resistant germ plasm to maize head smut is studied in this experiment in various susceptible backgrounds on condition of manual inoculation. There is significant difference of resistance degree among generations. The susceptible ratio of F1 and F2 is between the two parents and inclines to the resistant one, and there is no heterobeltiosis among offspring. The susceptible descendant ratio is mostly inclined to the backcross parent when backcross is made between F1 and their parents. The inheritance of maize head smut is in accordance with six parameter model and four-parameter model, and the main genetic effects are additive effect and dominant effect. But there is evident epistatic effect and overdominance effect in the background of the maize variety Huangzao 4, and there is only additive effect and dominant effect in the maize variety 3788, which are almost equal. There is at least 1 pair of resistant gene in the cross of which one parent is Mo 17, and the calculation gene pair is 0.48~1.03.