Early maturing varieties ‘Xiang K27’ and ‘JX0010’ were used as test materials with the control conventional late maturing varieties ‘HN127’ in this study, two densities(2000 plants/(667 m2), 3000 plants/(667 m2)) and two sowing dates(May 25, June 5) were set up to conduct field experiments in the Hunan Agricultural University farm base in 2021. The physiological and biochemical indices and yield components were collected to investigate the effect of planting densities and sowing dates on the cotton yields. The results showed that the SPAD value of early maturing direct seeding cotton was higher, and the SOD activity was lower. Compared with early sowing, late sowing could significantly improve the SOD activities of different cotton varieties from bud stage to flower and boll stage. From the POD activity, early maturing cotton was the best. From the MDA content, under the conditions of early sowing and high density, the conventional late maturing varieties were the best at the vegetative growth stage(bud stage), and the early maturing varieties were the best at the reproductive growth stage(flower and boll stage). Different varieties significantly affected the single boll weight and number of bolls per plant, and then significantly affected the cotton yield. Early maturing varieties were superior to conventional late maturing varieties, and the yield of early maturing cotton was the highest. Comprehensive analysis showed that early sowing could improve the yield of early maturing cotton. Although the density could make up for the yield loss to a certain extent, the potential was small.