Under cold damage circumstances in Kunming,the cold tolerance at the booting stage of BC_5F_1,BC_5F_2,BC_5F_3 and BC_5F_4 generation of hybrids from near-isogenic line(BC_4F_5) of parents Lijing2(japonica rice) and Towada(indica rice) was analyzed by using major gene-poly-gene mixed inheritance models.The results showed that:(1)In the same generation,filled grains and total grains,seed setting rate of BC_5F_2,BC_5F_3 and BC_5F_4 populations were significantly positive correlated.(2)With cold tolerance indentified index of seed setting rate,cold tolerance at the booting stage of NIL were controlled by two major genes plus polygenes,while heritability of major gene was 90.97%,heritability of polygene was 3.83%,and both the independent two major genes and polygenes had additive-dominance-epistatic effects.