Abstract: 【Objective】 To explore the rule of the growth and yield formation of cotton under drip irrigation in northern Xinjiang with different concentrations of ethephon compound reagent, to seek the optimal concentration combination, and to provide theoretical basis for the application and promotion of cotton chemical topping technology. 【Method】 Luyanyan 24 was used as the test variety, and 5 ethephon with different concentrations (C₁: 0 mg/L, C₂: 100 mg/L, C₃: 200 mg/L, C₄: 400 mg/L, C₅:800 mg/L) combined with unidazole to study the effects of different compound reagents on the growth and yield formation of cotton under drip irrigation in northern Xinjiang. 【Result】 Compared with C₁ treatment, the final length of new main stem was reduced by 10.9%-34.67% in other treatments.Compared with CK, plant height was significantly increased by 10.55%-21.26% under C₁, C₂, C₃ and C₄ treatments.Each treatment significantly increased fruit branches by 1.9-2.7 and leaf age by 2-3.2.Under C₄ and C₅ treatments, internode length was significantly reduced by 7.21% and 7.75%, respectively.Under C₃ treatment, SPAD value was significantly increased by 8.22% and 8.46% on 101 d and 125 d after sowing, respectively.The dry matter weight of leaves, stem and reproductive organs under C₃ treatment significantly increased by 16.97%, 14.57% and 38.68%, respectively, in the late bolling stage.The dry matter weight of leaves, stem and reproductive organs under C₃ treatment significantly increased by 22.56%, 13.92% and 36.6% in the stage of bolling.Under C₃ treatment, the boll-forming rate of the upper part was up to 47.5%, which increased by 36.67%, and the boll number per plant was significantly increased by 18.18%.Under C₃ treatment, the seed cotton yield was significantly increased by 17.64% and 880.5 kg/hm². 【Conclusion】 The combination of ethephon and enbulobuzol could control the plant height, increase the number of fruit branches and leaf age, shorten the internode length of main stem, increase the SPAD value, increase the dry matter weight of each organ, promote boll formation in the upper part of cotton plant to a certain extent, and finally increase the yield.All things considered, the ethephon concentration at 200 mg/L combined with enlobuzole effect is the best, which can be used for cotton chemical topping.