【Objective】The study aimed to assess and determine the P loss risk in red soil profiles of sloping upland and paddy fields based on the variation of soil phosphorus storage capacity (SPSC). 【Method】The soil samples were collected from different pedogenic horizons in peanut uplands and paddy fields which were located at the top, middle and bottom of the slope in Sunjia small watershed, Ying tan, Jiangxi province of China. The profile variation characteristics of total P(TP), soil available P(Olsen-P), P saturation rate (PSR), P sorption index (PSI) and SPSC of tested soils were analyzed. Also, the effects of soil total carbon, total nitrogen, iron-aluminum oxides, pH, Eh and bulk density (BD) on the P loss risk of red soil profiles at different slope positions were evaluated. 【Results】Soil TP and Olsen-P of the surface layer in peanut uplands and red paddy fields were significantly higher than those in the bottom layers and the profile variations of TP and Olsen-P in paddy fields were significantly higher than those in peanut uplands. Compared with the Ap1 layer, the PSI of peanut upland in the subsurface soils increased significantly by 33.1%~146%, and the PSI decreased with the increase of profile depth, but the PSI of paddy fields increased significantly with the increase of profile depth. The soil PSR of peanut upland and paddy field(except PF-M)decreased gradually with the increase of profile depth, while the variation ranges of SPSC were -89.2~298.3 mg·kg^-1 and -138.1~101.1 mg·kg^-1, respectively. The SPSC values of PU-T and PU-M were all positive, and they decreased with the increase of profile depth. Also, the SPSC value of all pedogenic horizons in PU-B(except Ap2)were all negative. The SPSC values of pedogenic horizons in PF-T (except Brs), PF-M (except Ap1), and PF-B were negative, and they changed significantly with the increase of profile depth. 【Conclusion】Based on the assessment of soil phosphorus storage and its environmental loss risk in sloping red soil profiles by SPSC theory, the migration and transport signs of soil P in peanut upland along the profile and slope position are obvious. Once soil Olsen-P > 27.6 mg·kg^-1, the risk of soil P loss in the peanut upland profiles will increase sharply, and control measures should be taken in time. The risk of P loss exists in each soil profile of the paddy fields, thus, proper management practices should be implemented during the application of P fertilizer.