Abstract: By setting different seeding rates to regulate the population density of rapeseed, the differences in population growth and development, yield formation, and economic benefits were analyzed to determine the appropriate seeding rate of rapeseed for providing reference for high-yield cultivation of rapeseed under flying inter-planting in rice triple cropping system in Jiangxi Province. This experiment was conducted with 2 early maturing rapeseed varieties: Ganyouza 906 and Zhongyou 988, and 5 seeding rates of 4.5, 6.0, 7.5, 9.0 and 10.5 kg∙hm⁻². The results show that with the increase of seeding rates, the population density increases significantly, while the leaf size, total leaf number and rhizome diameter decrease. The dry matter accumulation increases first and then tends to be stable. The lodging resistance and stress resistance are with the best value at 7.5 kg∙hm⁻² seeding rate. The yield and net income of Ganyouza 906 and Zhongyou 988 both show a trend of first increasing and then decreasing with the increase of seeding rates. The yield and net income of Ganyouza 906 are with the highest value at 6.0 kg∙hm⁻² seeding rate, which is 1 729.6 kg∙hm⁻² and 3 987.3 yuan∙hm⁻², respectively, and the input-output ratio is 1.62. The yield and net income of Zhongyou 988 are with the highest value at 7.5 kg∙hm⁻² seeding rate, which is 1 935.4 kg∙hm⁻² and 5 147.4 yuan∙hm⁻², respectively, and the input-output ratio is 1.80. Therefore, adaptive varieties should be fully selected, and the appropriate seeding rate is 6.0 - 7.5 kg∙hm⁻² under flying inter-planting in rice triple cropping system in Jiangxi Province.