Modeling heavy metal behavior in soil and water will provide a better understanding of the potential adverse impacts on human and ecological system. A heavy metal transport and transformation module was combined with the well-established Soil and Water Assessment Tool(SWAT)model to simulate the fate and transport of metals at the watershed scale. The heavy metal module accounts for sorption and slow reactions among categorized metal species. Heavy metal transport in the upland is modeled based on water percolation,rising, runoff, and soil erosion; while in the water body, heavy metal undergoes settling, resuspension, diffusion and burial processes. The SWAT model combined with heavy metal module(SWAT-HM)was used to simulate zinc(Zn)and cadmium(Cd)dynamics in the upper Liuyang River basin. The simulations were reasonably accurate, with 94.5%(Zn)and 94.2%(Cd)of the prediction-to-observation ratio below a factor of 10.It also agreed well with other monitoring data by reproducing the high metal concentrations and their drop before and after the Baoshan- Daxi confluence, and by revealing the dominance of precipitation events in terms of watershed metal exports. To account for the effects of climate change on heavy metal pollution, we also simulated the Zn and Cd output from the studied watershed under nine meteorological scenarios, each with either the temperature or the precipitation intensity adjusted from recorded values. We found that the metals were more sensitive to precipitation than temperature, and that particulate metals responded more strongly than dissolved metals. Our results showed that SWAT-HM is a powerful tool for watershed-scale environmental risk analysis and pollution control in the context of climate change.