The primary purpose of this research was to give suitable irrigation program according to the growth period and water requirement. A cotton field experiment with mulched drip irrigation was conducted at the National Field Observation and Research Station for Oasis Farmland Ecosystem in Aksu of Xinjiang in 2008. Water balance method was adopted to study the water requirement and water consumption law of cotton under mulched drip irrigation in Tarim Irrigated Area. Statistical analysis of experimental data of irrigation indicates that the relationship between yield of cotton and irrigation presents a quadratic parabola. We fit the model of cotton water production on the basis of field experimental data of cotton. And the analysis on water saving Benefit of cotton under mulched drip irrigation was done. Results indicate that water requirements for the irrigated cotton are 543 mm in Tarim Irrigated Area. The water requirements of seedling stage is 252 mm, budding stage is 186 mm, bolling stage is 316 mm and wadding stage is 139 mm. the irrigation amount determines the spatial distribution of soil moisture and water consumption during cotton life cycle. However, water consumption at different growth stages was inconsistent with irrigation. Quantitatively, the water consumed by cotton decreases upon the increase of irrigation amount. From the perspective of water saving, the maximal water use efficiency can reach 3 091 m3/ha. But the highest cotton yield needs 3464 m3/ha irrigation water. In summary, compared to the conventional drip irrigation, a number of benefits in water saving and yield increase were observed when using plastic mulch. At the same amount of irrigation, the cotton yield with plastic mulch was 30.2% higher than conventional approaches, and the efficiency of water utilization increased by 30.2%. While at the same yield level, 29.3% water was saved by using plastic mulch, and the efficiency increased by 41.5%.