In this paper, for the magnetic shielding problem of the multilayer infinite metal plates to the circular antenna, the Maxwell equations are solved strictly by the method of separating variables. Finally, the analytical formula of the magnetic shielding effectiveness of the multilayer plates is derived and programmed.The calculation formula of shielding effectiveness of multilayer metal plates is simplified to single-layer metal plate, and the result is consistent with Moser's formula of shielding effectiveness of single-layer metal plate. The influence of the position, the order and the gap between the multilayer plates on the shielding effectiveness is analyzed. The results show that the shielding effectiveness is independent of the position of the multilayer plates when the thickness and order of the metal plate, the position of the circular antenna and the observation point are unchanged. When the position of circular antenna, metal plate and observation point is constant, reversing the order of the multilayer plates does not affect the shielding effectiveness. When the frequency is lower than 10 kHz, the effect of the gap between the multilayer plates on the shielding effectiveness is small. When the frequency is higher than 10 kHz, the larger the gap between the metal plates, the greater the shielding effectiveness.