Objective To investigate the characteristics of runoff-phosphorus loss hysteresis relationship under different rainfall types.Methods This study focused on the Menglianggu small watershed in the rocky mountainous area of northern China. Using data from 32 rainfall events recorded between 2010 and 2012, C-Q (concentration-discharge) loops and Pearson correlation analysis were applied.Results 1) During torrential rain, a large amount of phosphorus was released after soil saturation, causing the phosphorus concentration peak to lag behind the runoff peak. In the case of heavy rain, dissolved phosphorus was released from nearby sources, while particulate phosphorus was transported from distant sources to the runoff. During moderate rain, the transport of DIP (dissolved inorganic phosphorus), PP (particulate phosphorus), and TP (total phosphorus) was mainly influenced by surface runoff, whereas DP (dissolved phosphorus) was affected by soil and sediment. Light rain showed rapid transport of DP and slower transport of PP. 2) The C-Q loops of phosphorus transfer exhibited various patterns during the runoff process. PP and TP often showed a clockwise lag, accounting for 18%—23%, mainly due to the strong scouring of surface runoff. The counterclockwise lag appeared in 12%—18% of the phosphorus components, resulting from the slow release of soil phosphorus and the resuspension of riverbed sediments. Dissolved phosphorus loss mainly exhibited a figure-eight positive loop, accounting for 16%, while DIP loss showed a figure-eight negative loop, accounting for 19%. Linear lags were less frequent, and complex lags ranged between 31% and 45%. 3) Under torrential and heavy rain conditions, DIP and DP had weak or negative correlations with runoff (Q), attributed to the rapid surface scouring, which caused PP to be more easily lost, while DP was adsorbed by the soil or diluted by the runoff. Under moderate rain, the appropriate runoff scouring force enhanced the releases of DP. In light rain, runoff primarily transported PP attached to loose soil particles. Particulate phosphorus and total phosphorus were consistently highly correlated across different rainfall types, indicating that TP mainly originated from PP.Conclusion The Menglianggu watershed needs to be protected against phosphorus loss for different rainfall conditions.