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Soil phosphorus (P) loss risk and environmental impact can be assessed by different soil test indicators such as soil P storage capacity (SPSC), a site-specific and reliable measurement of soil P status. In this study, the changing trends of soil P saturation ratio (PSR) and SPSC in red soil (equivalent to Ultisol) were discussed after 10 consecutive additions of P solution with 20 mg P L−1, and the relationships between Olsen-P, CaCl2-P, and PSR, SPSC also were evaluated. Results showed that the soil PSR was increased to 0.22 at the end of P addition, and the accumulated P was high to 1625 mg kg−1. The threshold PSR of the red soil was determined to be 0.10, and the SPSC significantly decreased from 242.0 mg kg−1 to −382.1 mg kg−1 with the increase of P addition times. When SPSC = 0, the accumulated P in red soil was 487.7 mg kg−1. Therefore, there existed four stages for the soil P management in red soil according to the changes of SPSC and Olsen-P: short supply stage of soil P (SPSC>88 mg kg−1 and Olsen-P ≤ 20 mg kg−1), stable supply stage of soil P (68 mg kg−1< SPSC≤88 mg kg−1 and 20 mg kg−1< Olsen-P ≤ 40 mg kg−1); over supply stage of soil P (0< SPSC≤68 mg kg−1 and 40 mg kg−1< Olsen-P ≤ 108 mg kg−1), and the high loss risk stage of soil P (SPSC≤0 and Olsen-P > 108 mg kg−1). In the last stage, P fertilization must be stopped and environmental protection measures must be taken immediately. [ABSTRACT FROM AUTHOR]