To explore the effect of symbiotic periods and densities on the growth and yield of rapeseed intercropping cotton, a split-plot experiment with three symbiotic periods [10 d (T10), 20 d (T20), and 30 d (T30)] and four levels of densities [30×104 (D1), 45×104 (D2), 60×104 (D3), and 75×104 plants ha–1 (D4)] was designed. The results showed that: (1) Prolonging symbiotic periods was favorable for rapeseed growth in terms of the number of green leaves, LAI, root biomass, aboveground biomass, root-shoot ratio, plant height, crown diameter all increased, whereas angle of stem lodging decreased. These led to increase in yield both single plant and unit hectare. (2) The effects of plant density on rapeseed growth and yield depended on the symbiotic period. The number of green leaves, root biomass, aboveground biomass decreased with plant densities, which resulted in decreased yield per plant. At T30, the maximum LAI was observed under D3, while it was increased with plant density at T20 and T10. The population yield had the same trend with LAI. The yield reached the maximum when the symbiosis period was 30 days and the plant density at 45×104 plants ha–1,whereas the angle of stem lodging reached the minimum at T30D3. (3) Based on the regressions, for Wuxue sites, the optimum symbiotic period was 29.8 days and the optimum plant density was 48.8×104 plants ha–1 while these for Tianmen were 29.7 days and 57.6 plants ha–1. Under these arrangements, Wuxue and Tianmen could achieve the yield about 3243.0, 3082.8 kg ha–1,which were increased by 23.5%, 17.4%, respectively, when compared to the traditional arrangement (the symbiotic period was 15d, the plant density was 15.0 to 22.5×104 plants ha–1 and the average yield was about 2625 kg ha–1).