The effects of potassium(K) application rates on the yield, quality and K fertilizer use efficiency of three hybrid cotton varieties (Jin102, Xiangzamian No. 8, Siyang328) were studied in field experiment. Fertilizer rates of K2O from 135 kg/hm2 to 270 kg/hm2, representing 1x and 2x recommended K rates, were applied, no application of K fertilizer as the CK. The results showed that the lint yield increased 39.13%–57.48% with potassium application, highly significantly. All yield components of the three hybrid cotton varieties increased as K application rates increased. The boll number, single boll weight and lint percentage per cotton plant increased by 14.24%–40.29%, 3.59%–15.51%,and 0.16%–4.89% respectively.. The partial factor productivity (PFPk) reduced by 45.93%–48.01%, the agronomic efficiency (AEk) reduced by 37.1%–42.9% in 2x. The PFPk and KE (K efficiency coefficients) of S328 were the highest among the three varieties, and its resistance to low potassium stress was the strongest, without potassium fertilizer application (K0), its lint yield was 5.54% and 11.19% higher respectively than that of the other two varieties. The AEk of J102 was the highest, and its reward of K fertilizer was the greatest among the three varieties. The specific strength and fiber length increased with the increase of the amount of potassium fertilizer application no significant differences for micronaire among K application rates. were discovered.