Abstract: The affinity of self-incompatibility in the mustard family affects the purity of hybrid seed and the propagation coefficient of stock plant.The result showed that the different positions of the flower-ing branch caused different affinity index.Generally,the fruiting index of self-crossing was low and sta-ble at the middle and lower branchs of plant and high at the upper branchs. It was also affeted by its nutritional conditions. There were low and stable index in the vigorous plants,otjerwise,it was gigh.Besides,it was affected by the flowering age. The index was high during the bud stage of the flowering,the highest index appeared in 2-4 days before flowering.Afterwards,it reduced gradually to zero in the stage of flower desclinning.