Abstract: 【Objective】 In order to determine the suitable planting density of JI JC4 and JI JC7 in Hebei cotton area, the effects of different planting densities on growth and development, yield, quality and disease resistance were studied. 【Methods】 4 different planting densities (4.5×10⁴, 9×10⁴, 13.5×10⁴ and 18×10⁴ plant/hm² ) were set to investigate the agronomic traits, yield, quality and disease resistance of cotton, and the optimum planting densities of JI JC4 and JI JC7 were comprehensively analyzed. 【Results】 With the increase of planting density, the plant height of JI JC4 and JI JC7 decreased, the height of the first node of fruit branch increased, and the whole growth period delayed. The lint yield of JI JC4 was higher with the increase of planting density, and the difference was obvious. The density of JI JC7 line had little effect on lint yield. Different planting densities had effect on micronaire value of JI JC4, on elongation of JI JC7, and had no significant effect on other cotton fiber quality indexes. With the increase of planting density, Verticillium wilt disease index decreased and its resistance increased. 【Conclusion】 Overall, the suitable planting density of JI JC4 and JI JC7 were 13.5×10⁴ plant/hm².