The Tongshanyuan Reservoir, located in southwest Zhejiang Province, serves as a crucial water supply and irrigation source but is currently facing significant heavy metal pollution. To develop effective pollution prevention and control measures and ensure the well-being of the population within the water resource radiation area, seven sampling points were designated within the reservoir. The contents of Cd, Cr, Cu, Ni, Pb, Zn, Hg, U and other heavy metals were determined using an inductively coupled plasma mass spectrometer. Principal component analysis was employed to analyze the distribution characteristics of pollution while potential ecological risk assessment methods were used to evaluate its impact on the ecosystem. The results revealed varying degrees and ranges of heavy metal contamination in the sediment of the reservoir with severity ranking as follows: S7 > S3 > S4 > S6 > S2 > S5 > S1. Pollution primarily concentrated in densely populated areas with frequent human activities along Right Branch Stream and Duze Town. Notably severe contamination was observed for mercury (Hg) and cadmium (Cd) in sediment samples which posed high potential ecological risks originating mainly from agricultural pollution upstream of Left Branch Stream and industrial pollution upstream of Right Branch Stream. Appropriate control measures can be implemented to mitigate heavy metal pollution levels in order to safeguard both aquatic ecosystems and human health.