This paper presents one efficient and accurate EMI shielding performance simulation method for metal particles coated on nonwoven textile-based material with the optimized textile module using the finite element method (FEM) simulated in the waveguide model. Copper particles coated polyester nonwoven materials with three contents of copper were made by the electroless plating method, which was used to evaluate the results from the EMI shielding test and simulation run. The mean absolute percentage error (MAPE) and p-value from the two samples' t-tests show that the simulation results of the two samples are less than 6.08%, and the p-value is more than 0.05. For the rest of one sample, the error of simulated value to measured value is higher (<10%) caused by the low copper content. By adjusting the parameters, the simulation result shows that reduce 10% of the sample porosity, the SE at 1.5 GHz is increased from 7.7% to 9.9%, which is the preferred method to increase the SE compared to adjusting the coating material.