Abstract: To investigate how cucumber leaf size is geneticially determined，two parents with signicantly different leaf size，namely‘SJ57-h’（small leaf，‘P1’hereinafter）and‘SJ11-1’（big leaf，‘P2’hereinafter），were used to generate F1，B1，B2 and F2 populations for joint analysis，using mixed major gene plus polygene inheritance model in different seasons. The results showed that the leaf size was controlled by two additive-dominant-epitasis major genes plus additive-dominant-epitasis polygenes（E-0 model）. Leaf size was closer to P2（big size）. In spring，the major gene heritability of B1，B2 and F2 wereestimated to be 75.1%，26.59% and 61.19%，respectively，with the heritability of polygene as 0.36%，55.41% and 21.39%，respectively. The variance of the environment accounted for 25.03%，73.79%，39.01% of the phenotypic variation of three generations，respectively. In autumn，the major gene heritability of B1，B2 and F2 were estimated as 80.16%，34.82%，86.59%，with the heritability of polygene being 0，49.18% and 0，respectively，and the variance of the environment accounted for 20.43%，65.48%，13.51% of the phenotypic variation，respectively. It indicated that cucumber leaf size was dominated by major genes while environment factors also play a great role，espcially on the B2 generation. In practice，high hereditability of major genes is favorable to an efficient selection in early generation of F2 and B1 for suitable leaf size in cucumber breeding.

Key words: cucumber, leaf size, major gene plus polygene, inheritance model