Abstract: In order to investigate the application effect of a new defoliation ripening agent Xinsaili, on medium early-maturing cotton （Gossypium spp） varieties in the cotton-planting area of Poyang Lake, the field experiment wascarried out with Ganmianza No.1 as test material. The results showed that the defoliation and ripening treatment had very good defoliation effect. After 15 days of spraying, the defoliation rate could reach above 95.0%, and when sprayed for 25 days, it could reach 100%. The ripening effect was thiophenone 750 g+ethephon 2 700 mL/hm² was the best treatment, followed by 2 700 mL/hm² Xinsaili treatment. The defoliation ripening treatment could significantly increase the yield of prawn cotton, including thiophenone 750 g+ethephon 2 700 mL/hm² treatment was the highest, followed by 2 700 mL/hm² Xinsaili treatment. Each defoliation ripening treatment had no significant effect on single boll weight, single boll housing weight, clothing score and fiber quality. There was no effect on the germination of cotton boll seed with a bell period of more than 50 d during spraying. In summary, under the same climate and geographical conditions in Poyang Lake planting cotton area, the same application techniques as those of early-maturing varieties are applied to the mid-early maturity varieties, and the defoliation ripening effect is ideal, indicating that the appropriate dose of Xinsaili（1 800~2 700 mL/hm²） can be used for defoliation and ripening of medium early-maturing varieties.

Key words: cotton （Gossypium spp）, defoliation ripening, medium early-maturing, Xinsaili, Poyang Lake planting cotton area