Abstract: 【 Objective 】 The objective of this research is to investigate the effects of chemical topping with mepiquat chloride(1,1-dimethyl-piperidinium chloride, DPC)on main agronomic and yield traits of cotton in the hope of providing theoretical support for the chemical topping technology in southern Xinjiang of China. 【 Methods 】 Field experiment was carried out in the 16 th regiment of Alar, southern Xinjiang during growing seasons of 2019. With manual topping as the control, a completely random design was adopted to study the effects of different concentrations of DPC (0, 90, 180 and 270 g/hm²) on cotton plant height, length of new main stem, number of new sympodials, yield and yield components. 【 Results 】 Compared with manual topping, the plant height of DPC chemical topping increased by 7.9-28.5 cm, the length of the new main stem increased by 8.8-22.3 cm, and the number of new fruit branches increased by 3.6-5.0. The high-rate of DPC (270 g/hm²) could increase the dry matter and accumulation rate of boll. Chemical topping did not affect boll weight and lint percentage. The high-dose of DPC (270 g/hm²) showed a slight decrease of 2.4% to the manual topping. 【 Conclusion 】 The application of DPC with 270 g/hm² for chemical topping in southern Xinjiang of China can not only obtain better consequent, but also will not reduce the yield of cotton.