Abstract: Three-year-old potted apple trees (Malus domestica Borkh. cv Red Fuji)/Malus hupehensis were used to study the effects of main branch bending on characteristics of distribution of 13C and 15N，and as well as utilization of 15N. The results show that the 13C distribution ratios in roots decrease significantly with the increase of main branch bending angle, an the values of 13C distribution ratios in roots of control, branch horizontal and branch drooping are 46.39%，36.39% and 26.73% respectively at the autumn shoot growing stage. There is a significant positive correlation between13C distribution ratio in leaves and the bending angle, and 13C distribution ratio in leaves of the control, branch horizontal and branch drooping are 30.15%，42.40% and 54.97% respectively at the autumn shoot growing stage. The 15N utilization ratio of treated plants is lower than that of the control, the significant difference is found at the autumn shoot growing stage, and the ratios of the control, branch horizontal and branch drooping are 5.29%, 3.87% and 4.05%. The 15N distribution ratio to spring shoots of the treated plants is significantly lower than that of the control, while the ratio to leaves is significantly higher than that of the control at both the spring shoot and autumn shoot growing stages, The 15N distribution ratios to new shoots and perennial organs of the treated plants are significantly lower than those of the control at the spring shoot stop growing stage.