A soil column culture experiment was conducted under the ecological and climatic conditions of Xinjiang to study the effect of water content in root zone on root growth, vigour and yield of cotton with the cultivars of different water-sensitivity Xinluzao 6 and Xinluzao 8 under drip irrigation with film mulching. The results indicated that the water content in root zone of 50%～55%, respectively, of field water-holding capacity before drip and 70%～75% after drip inhibited root growth and reduced root biomass. However, the root vigour and biomass in layer of 40～100 cm were enhanced under the water content condition. Furthermore, it reduced the root/shoot ratio and increased economic index that led to high yiled of cotton. The differences of response to drip irrigation among varieties were great, seed yield of Xinluzao 8 was higher in convention and sufficiency drip irrigation than that of Xinluzao 6.however,under limited drip irrigation Xinluzao 8 was significantly lower than Xinluzao 6. It will be of great importance to institute the optimum irrigation schedule under the condition that the dripping cycle is 7～8 d and the dripping quantity is 375 ～450 m~3·hm~(-2), according to the differences of response to soil moisture content among varieties for abstaining high yield and high water use efficiency.