Abstract: Using 3×4 incomplete diallel，two combinations of different genetic background in five generations are evaluated with GAV plant strain The results show that the hereditv effects of resistance to BYDV are additive，dominant and epistatic，and the additive effect is the majority．Heritability in a broad sense is over 90％．and that in a narrow sense is 75％ ～83％，Express variations in progenes of the two combination are different because of their different parents．The progenes’average resistance and depth of separation are close to the male’s resistance and coefficient of variation．