During staged fracturing in horizontal wells, casing perforations are subjected to high pumping pressure, high flow velocity, and high proppant concentration, by which severe erosion can readily be induced. As a result, casing wall thickness is reduced, perforations are enlarged and deformed, and the effectiveness of limited-entry fracturing is significantly impaired. To quantify the erosion characteristics of casing perforations, a CFD-DDPM (Computational Fluid Dynamics-Dense Discrete Phase Model) approach is employed to establish a casing perforation erosion model. Simulations are carried out to investigate perforation erosion under various influencing factors. The erosion mechanism is clarified, and the effects of pumping rate, proppant concentration (sand concentration), perforation flow split ratio, fluid viscosity, proppant size, and perforation angle on the erosion rate and erosion area are determined. It is shown that at low impact angles (0°-35°), ploughing and chip formation are produced by cutting wear, whereas at high impact angles (near-normal incidence), impact craters are caused by deformation wear. When the fracturing fluid viscosity is below 20 mPa·s, an increase in the erosion rate with viscosity is observed; above 20 mPa·s, a slower increase in both erosion area and erosion rate is caused by the attenuation of flow resistance and turbulence. To balance fracture conductivity against erosion risk, it is recommended that the proppant concentration be maintained at approximately 15%, and that proppant with a particle size of 0.212 mm be preferentially used. Additionally, relatively greater erosion intensity is observed in downward-oriented perforations. For an individual perforation with an excessively high flow split ratio, temporary plugging technology can be applied to isolate the dominant perforation, whereby its excessive erosion is prevented. From these findings, theoretical guidance is provided for predicting perforation erosion severity and optimizing fracturing parameters.