In order to make it clear the effects of heavy metals in the soil of mining area to its surface water around, taking the Pengcun Reservoir on the Chanxi River which is a branch of Minjiang River as an example, a twodimension heavy metal prediction model was set up based on the MIKE21 model. According to the principles of migrationdiffusion, suspensiondeposition and adsorptiondesorption of heavy metals in water and sediment, and by using the concentration data of heavy metals in the reservoir area obtained from the experiment of soil leaching and immersion, the contamination distribution of heavy metals such as Zn, Cd and Pb under different reservoir inflow was simulated. The results show that the distribution order from small to big of Zn concentration under a low flow condition is the central zone of reservoir,river banks,the places close to mining area, while under a high flow condition, the order from big to small is the central zone of reservoir, river banks and downstream, upstream; the distribution order from big to small of Pb concentration is the central zone of reservoir, river banks and downstream, upstream; the distribution order from big to small of Cd concentration is the central zone of reservoir, river banks and downstream, upstream; after reservoir impounding, the concentration of heavy metals in the reservoir can basically meet the water quality standard of Class II in GB3838—2002 surface water environment quality standard.