The conventional japonica rice and its Cry2A^* transgenic rice lines， and the conventional indica rice and its Cry2A* transgenic rice lines were used to conduct the pot experiment. The root characteristics of Cry2A^*transgenic rice lines under nitrogen application and no nitrogen application were investigated to study the root characteristics of Cry2A* transgenic rice lines and provide technical support for the cultivation and regulation of insect-resistant transgenic rice. The results showed that the root length， root surface area and root volume of the Cry2A* transgenic rice lines were significantly lower than those of the parents under no nitrogen application at the stage of mature， but there was no significant difference between them and the parental control under the nitrogen application. The root active absorption area of KY（Cry2A*） was significantly higher than that of the parents at the stage of flowering， while the root active absorption area of MH86（Cry2A*） was not significantly different from that of the parents. Compared with no nitrogen application， nitrogen application significantly increased the root diameter of KY（Cry2A*）， but had no significant effect on the root diameter of MH86（Cry2A*）. It is indicated that there was a certain difference in the root characteristics between the Cry2A* transgenic rice and its parents， and this difference was more obvious under no nitrogen application.