With the experiment method of combining simple hollow with field plots, the effect of development of cotton and its yield was studied preliminarily by irrigation amount per time. The results showed that through coordinating development progress, the irrigation promoted the cotton development at the right amount and right moment, the boll productivity increased in 0.9~1.8 per plant, boll weight increased in 0.23~0.39g, lint percent increased in 0.6~1.3% and total lint yield increased in 15.7%~28.1% compared with that of no irrigation growing field. Irrigation efficiency came to 0.26~0.44kg/m3. However, yield effect was not in direct proportion as amount of irrigation. The cotton overgrowth was coursed by over-irrigation, which reduced yield. According to economic effect, the irrigation amount, which is 450~675m3/hm2, is better from first-flowering time to height-flowering one.