This study focused on the correlation between river sinuosity and self-purification capacity, using the Shiwuli River in Hefei, China, as a case. Through field monitoring, the reduction rate of each pollutant per unit length of river reach and its correlation with the corresponding sinuosity were analysed. The results show that river sinuosity has different degrees of positive correlation with the growth rate of dissolved oxygen (DO) and the reduction rates of total nitrogen (TN), ammonia nitrogen (NH3-N) and total phosphorus (TP). River sinuosity needs to be above 1.42 to ensure the river's basic self-purification capability. We also discuss the mechanism of river sinuosity on water body self-purification and propose the increase in river sinuosity to improve the river's capacity to purify water from pollutants. This measure could enhance the growth rate of DO, the longitudinal hyporheic exchange flow, and the action time of other basic self-purification factors of the river. This study could help scientific decision-making in river reconstruction planning in the process of urbanization in the middle and lower reaches of the Yangtze River in China.