Irradiation can cause changes in the composition of silver-indium-cadmium (Ag-In-Cd) control rods, thereby affecting their lifespan. In this study, a Monte Carlo simulation was used to model the variation in the chemical composition of Ag-In-Cd control rods over irradiation time. By analyzing the neutron absorption characteristics of the control rods, the trends of chemical composition changes in the radial direction of the control rods were investigated. Additionally, based on the impact of control rod insertion on the axial power distribution, the chemical composition changes of Ag-In-Cd control rods in the axial direction were also simulated and analyzed. The analysis results indicate that with increasing irradiation time, the production of cadmium and tin in the outer layer of the control rod is significantly higher than in the inner layer. Moreover, the production of cadmium and tin at the lower end of the control rod is notably higher than at the upper end.