Abstract: Taking the Bijiang River as an example, in order to reveal the characteristics of the migration and change of the heavy metals Zn, Pb and As in the water bodies of small and medium rivers, the impact of the Jinding Lead-Zinc Mine is mainly considered. Based on the analytical data of 15 water samples from the upstream to downstream areas of the mine, combined with the hydrodynamic characteristics of the migration and transformation of heavy metals in the water body, the comprehensive attenuation coefficients K of Zn, Pb and As in the water were determined by the method of trial and error. A simulation model suitable for the migration and transformation of Zn, Pb and As in the Bijiang River was established by using MATLAB. The results showed that: ① The comprehensive attenuation coefficients K of the heavy metals Zn, Pb, and As in the lower reaches of the Jinding Mining area in the Bijiang River Basin during the dry season are respectively, 0.015 per second for the whole process of Zn, 0.006 per second for Pb and 0.018 per second for As in the upstream of Golang Village, 0.004 per second for Pb and 0.002 per second for As in the downstream. ② The simulated values of Zn, Pb and As contents in the downstream water body of the mining area fit well with the measured values, and the simulation equation has certain practicability. ③ Simulating the changes in the mass concentration of heavy metals Zn, Pb, and As in the water during the high water period of the Bijiang River can also be verified by re-calibrating the comprehensive attenuation coefficient K or supplementing the sampling data of individual samples to further optimize the simulation effect. The research conclusions can provide a scientific basis for environmental pollution control and ecological restoration in the Bijiang River Basin.