The economies of scale in cotton production should suit local conditions, and the mastering of Xinjiang farmers' cotton-growing situation has great significance to guide their planting and cultivation. By questionnaire, this paper researched the cotton production costs, economic efficiency planting acreage and others on Akesu in Southern Xinjiang, Changji in Northern Xinjiang and Turpan area in EasternXjinjiang, evaluating their cotton economies scale separately and collect the data to summarize the optimal production area in whole province. The results show that, in Changji city, with the increase of planting area, the cotton production costs present decrease trends at first and then increase in a U-shape, the R² value is 0.332, the optimal planting area is 176.7 acres, while Turpan sample shows that when the area is 71.9 acres can obtain the minimal input costs 623 RMB, and in Akesu, when the planting area is 72.57 acres will costs lowest 827 RMB per acre. And the largest optimal planting area is theChangji city in Northern Xinjiang. Analyzing the collected data, the results shows that the optimal economy planting area in overall province is 330 acreages, and corresponding lowest production costs is 913 RMB. It suggests that there exits differences between various regions of farmers economics of scale in Xinjiang and the planting area in northern part is larger.