Abstract: A field experiment with three irrigation amounts and five nitrogen application levels was conducted to investigate the effects of water and nitrogen regulation on the growth characteristics, yield component factors, and water and nitrogen use efficiency of cotton in south Xinjiang under mulched drip irrigation. With the increasing amount of irrigation, the plant height, leaf number on main stem, boll number, LAI, and dry matter accumulation in leaf and stem improved significantly, but the root growth was restrained. As compared with low and high irrigation amounts (4950 and 6750 mm·hm^-2, respectively), medium irrigation amount (5850 mm·hm^-2) increased the available bolls per plant and the single boll mass averagely by 0.96 and 0.4 and by 0.22 and 0.11 g, respectively. When the nitrogen application level was 300 kg·hm^-2, as compared with other nitrogen application levels, the stem diameter increased significantly, and the growth of bud, boll, and root was accelerated. Moreover, the allocation ratio of dry matter from nutritional organs to reproductive organs under medium irrigation amount increased by 5.1% and 29.6% respectively, as compared with that under low and high irrigation amounts. Irrigation amount had significant effects on the cotton yield but little effects on the lint percentage, whereas nitrogen application level had definite effects on the cotton yield and lint percentage. However, low irrigation amount restrained the effects of nitrogen application on yield enhancement. In this experiment, when the irrigation amount was 5850 mm·hm^-2 and the nitrogen application level was 300 kg·hm^-2, the cotton grew healthily, the plant shape structure was optimized, the dry matter allocation to reproductive organs was promoted dramatically, the available bolls, single boll mass, and lint percentage increased, the cotton yield reached the highest (6992.33 kg·hm^-2), and the water and nitrogen use efficiency amounted to 1.45 kg·m^-3 and 45.9%, respectively.