According to the hydrodynamic characteristics of wide and shallow rivers and the transfer characteristics of soluble pollutants in rivers, a mathematical inverse problem about location and intensity of instantaneous pollution source in wide and shallow rivers is established. The solving method of this problem is given using differential evolution algorithm. A typical case is set out and the solving method is verified using the theoretical solution of concentration plane distribution of instantaneous pollution source. Based on the scene analysis method, further analysis is made to analyses the influence of monitoring sites and monitoring frequency on inversion accuracy of the pollution source. The results indicate that: the inversion accuracy depends on several influencing factors including the number of monitoring sites and monitoring frequency. The mathematical inverse problem of pollution source based on certain monitoring data and monitoring accuracy can provide technical support on determining the intensity and location of instantaneous pollution source.