Yuntian-930 is a wild melon that is highly resistant to powdery mildew (PM). To determine the inheritance of resistance to PM, Yuntian-930 was crossed with another cultivated melon, Hualaishi, which is susceptible to PM. Inheritance of resistance to Podosphaera xanthii race 2F. in six plant generations (P1, P2, F1, B1, B2, and F2) was studied using the mixed major-gene plus polygene inheritance mode with joint analysis method. Inheritance of resistance in wild melons fitted the model of two pairs of additive-dominance-epistasis major genes plus additive-dominant-epistasis polygene. The additive, dominant and epistatic effects between the two major genes played an important role in inheritance. The estimated values of heritability of major genes in B1, B2 and F2 were 62.98, 58.58 and 90.89% and those of polygene heritability were 28.93, 31.47 and 3.22%, respectively. The ratios of the environmental variance to phenotype variance were 5.89 to 9.94%. Thus, resistance of Yuntian-930 to PM was controlled not just by two major genes, but was also affected by polygene and the environment. The selection efficiency for a major gene of F2 was highest in the resistance breeding program. Key words: Wild melon, powdery mildew, resistance, P. xanthii race 2F, inheritance.