In order to explore the effects of different phosphorus rates on the root morphological parameters of maize and analyze their relationships to its phosphorus uptake in maize and soybean intercropping system，a pot experiment was conducted with two planting patterns(monocropped maize，maize and soybean intercropping)and four phosphorus rates [no phosphorus(0 mg/kg)，low phosphorus(50 mg/kg)，medium phosphorus(100 mg/kg)and high phosphorus(150 mg/kg)]. The results showed that compared with monocropped maize，maize and soybean intercropping significantly increased the root length，root surface area，root volume，root tip numbers and root dry weight by 24.17%，32.23%，35.01%，26.11% and 36.97%，respectively，and the average root diameter decreased by 17.74%，as well as the phosphorus uptake of maize plant increased by 58.94%. Meanwhile，the phosphorus uptake of intercropped maize under 50 mg/kg low phosphorus rate was not reduced compared to that of monocropped maize under 100 mg/kg medium phosphorus rate. The results of correlation analysis，path analysis and stepwise regression analysis suggested that there was a significant correlation between root morphological parameters and phosphorus uptake of maize，where root dry weight played a largest correlation relationship to phosphorus uptake of maize，followed by root surface area and average root diameter. These findings indicated that the increase of root growth，root surface area and the decrease of average root diameter were the important reasons for the improvement of phosphorus uptake capacity of maize in maize and soybean intercropping system.