Low soil phosphorus (P) availability and seasonal drought were the main limiting factors for soybean production in acid red soils of South China. Improving and screening P-efficient genotypes of soybean germplasm which could better adapt to low P soils and drought climate was one of the efficient approaches to increasing soybean yields. Pot experiment with P-efficient (BX10) and P-inefficient (BD2) soybean genotypes was conducted to investigate the effects of P application and water deficit on dry matter accumulation and phosphorus efficiency of soybean plants. Three rates of P application were P₀: 0, P₁: 15, P₂: 30 mg/kg soil, respectively. The two soil moisture treatments were 70%-80% of field water capacity ( FWC) as control and 30%-40% of FWC as drought stress at flowering and pod-setting stages respectively.The results showed that plant biomass and leaf chlorophyll content were increased, while root/shoot ratio of the two soybean varieties were decreased when soil available P increased; Drought stress increased root/shoot ratio of BX10 and BD2 at flowing and pod-setting stages under the same P application rate, but no significant effects were found on leaf chlorophyll content. Drought stress resulted in significant decrease of yield for both two varieties. Soybean yields in low P soils are significantly affected by medium P application (P₁ treatment), but much less and even negatively by high P application (P₂ treatment). The yield of BX10 was increased when soil available P increased, but the yields for BD2 in different P application rates were in the order: P₁>P₂>P₀. BX 10 had higher yield than BD2 under all phosphorus and water treatments. Whatever drought stress in flowering or pod-setting stage, root phosphorus efficiency ratio, P uptake efficiency and P transfer efficiency of plant were increased when available soil P increased, in contrast, P utilization efficiency was decreased with the increase of P application level. In total, BX10 had higher level in P absorption efficiency and utilization efficiency, while relatively lower level in root P efficiency ratio and P transfer efficiency than BD2.