Abstract:The Siheshui Watershed of the Tanjiang Valley, located in Jiangmen City, Guangdong Province, was used as the research region. Simultaneous monitoring of water quality and quantity during two rainfall events that occurred in May 2014 was conducted in order to study the characteristics and temporal and spatial variation of non-point pollutant emission in the rainfall-runoff process. The results show that the concentrations of pollutants such as BOD5, TP, and TN were high at the preliminary stage of the rainfall-runoff process, indicating a significant first flush effect. Soluble phosphorus accounted for a large proportion of the total phosphorus. The concentration of ammonia exhibited a first flush effect during the first half of the runoff process, and was negatively correlated with the volume of runoff during the second half of the process. The concentration of CODMn showed a wavy and jagged change trend, and in the later period the concentration was influenced by the water withdrawal process dominated by the interflow. The pollutant flux and the volume of runoff had an approximately identical change trend, and a remarkable correlation between them was detected through statistical analysis. There was no significant correlation between the output concentration of TSS and the concentrations of other pollutants, indicating that the suspended solids made a small contribution to the output concentrations of other pollutants. Based on experimental results and practical experience, recommendations are given for the basin’s management.