The insect-resistant inbred line 508 of the non-heading Chinese cabbage (Brassica chinensis L.)as female parent and susceptible inbred line 114 as male parent were used to construct six generation populations of P1、P2、F1、BC1P1、BC1P2 and F2. The resistances of all the populations to diamondback moth (DBM) were evaluated in net, and the joint analysis method for six generations was used to analyze the inheritance of insect-resistance. The results showed that the insect-resistance was partly recessive in the combination of 508×114 and fitted to the D-1 genetic model which is one pair of major additive-dominant gene plus additive-dominant polygene’s. The heritability of the major genes in BC1P1, BC1P2 and F2 populations were respectively 57.21%、25.87% and 76.05%. The results will be helpful for us to effectively utilize the insect-resistant gene resources in insect-resistance breeding.