Abstract: 【Objective】 In order to study the effect of the new defoliant Xinsaili in Kuytun area, the defoliation test was carried out with Z1146 as the test material. 【Method】 The defoliation rate, boll opening rate, yield and fiber quality of the new defoliant Xinsaili were studied by variance analysis and grey relational comprehensive evaluation. 【Result】 Spraying Saibenlong + ethephon (450 g/hm²+2,250 mL/hm²) and Xinsaili (1,800-2,700 mL/hm²) significantly improved the defoliation rate of cotton, and the ripening effect was better. In terms of cotton yield and cotton fiber quality, spraying defoliation had no significant effect on cotton fiber length, uniformity index and micronaire, but had certain effect on cotton yield and breaking tenacity. The comprehensive traits of all treatments were evaluated by grey correlation method. The order of comprehensive traits of different treatments was T₅ > T₄ > T₃ > T₆ > T₁ > T₂. The comprehensive evaluation value of T₅ treatment was the highest, which was 0.861,6. 【Conclusion】 T5 treatment (Xinsaili 4: 1,350 +1,350 mL/hm² sprayed two times) has superior comprehensive performance and is suitable for promotion in Kuytun cotton area.