The calculation of the former 5 layers stratified media theoretical model of HBC (Human Body Communication) takes too much calculation resource and time. To improve this condition, a simplified theoretical model of HBC based on the theory of waveguide on stratified media was proposed. According to the calculation results of theoretical and numerical models, attenuation constants in 5, 4 and 3 layers are consistent with each other, which is far from the results of 2 layers model. In conclusion, the model of 3 layers has been proved to maintain a balance between precision and efficiency in both theoretical and numerical approaches and can be used as the simplified theoretical model of HBC. The calculation time of the simplified theoretical model is just 0.215 times of the former 5 layers model without losing accuracy, which improves the efficiency of calculation by nearly 5 times. The simplified theoretical model is useful for the fast evaluation of the propagation mechanism of HBC signal.