Abstract: Stylosanthes is an important species for sod culture in orchards in south China. To alleviate nutrient competition by roots between Stylosanthes and fruit trees, it is necessary to screen Stylosanthes genotypes with appropriate root architecture. One experiment was conducted in specially designed rhizoboxes and another in pots. In the first experiment, the root architectures of seven Stylosanthes genotypes were investigated at normal P levels, and in the second experiment, P uptake efficiencies of two Stylosanthes genotypes with contrasting basal root angle were compared. Root architecture was characterized using scanning and WinRhizo analysis. There was a significant difference in root architecture among the seven genotypes. Plant biomass showed significant and positive relationships with total root length, tap root length, and root surface area. Based on plant biomass and root architecture, seven Stylosanthes genotypes were categorized into three classes. Two genotypes (‘Graham’ and ‘CIAT 184’) with high biomass and contrasting basal root angle were chosen for a further comparison of P efficiency. ‘CIAT 184’ had smaller basal root angles and a higher P uptake efficiency at high P level. However, at a low P level, P uptake efficiency was lower leading to a lower P efficiency. This study suggests that basal root angle is an important factor affecting P uptake efficiency, however, P efficiency also depends on plant growth performance at a low P level. ‘Graham’ is probably more suitable for inter-planting in orchards than ‘CIAT 184’.