Abstract: The objective is mainly about to study harmful regulation of cotton plant bug to cotton, and provide the theoretical ground for increasing cotton production. With the materials of N141 and Shi39 ,the authors studied that cotton plant bug occur regulation to two materials in different control conditions. The result showed :the main harm period were same, it was in July the last ten-day of a month to August the first ten days of a month, The damage was the highest under nature of control. The maximum percentage of boll shedding reached at 41.8%,the damage of cotton plant bug was not important after these days and before it .at the same time, the period is the yield formative time,the damage of the cotton plant bug have the direct relation in yield, the yield of nature control was reduce 39.3%~43.3% than integration prevention，the difference significantly.In order to save cost and improve yield, prevent cotton plant bug in main damage period in time