In order to explore suitable mode of nitrogen topdressing time on cotton under fruit tree and cotton intercropping in southern Xinjiang，an experiment was carried out with randomized block design to study the effects of nitrogen topdressing being brought forward on the accumulation of dry matter and nitrogen，nitrogen fertilizer use efficiency and yield under fruit tree shading.The experiment was performed with four nitrogen levels：N0（no nitrogen)，N1（nitrogen topdressing at initial flowering end of cotton)，N2（nitrogen topdressing at full flowering end of cotton）and N3（normal fertilization)，total nitrogen application was 270 kg/ha.Results showed that theoretical maximum accumulation of dry matter and nitrogen，maximum growth rate and growth eigenvalues of N2 were the largest.At the same time，nitrogen fertilizer use efficiency，nitrogen agronomy use efficiency，nitrogen partial productivity，nitrogen harvest index and maximum nitrogen momentary use efficiency of N2 were increased.Nitrogen topdressing at full flowering end was helpful to the accumulation and distribution of dry matter and nitrogen，the transformation from vegetative growth to reproductive growth and promotion of yield formation.The lint yield of N2 was higher than those of N0，N1 and N3 by 33.7%，17.4% and 10.7%，respectively.Thus，nitrogen topdressing should be appropriately brought forward to full flowering end（in the mid and last ten days of July)，it was benefit to increase of yield and nitrogen use efficiency under fruit tree and cotton intercropping in southern Xinjiang.