Abstract: To study the influence of isolation layer stiffness on the base isolation structure,and find the optimal stiffness of the isolation layer,friction sliding isolation steel plate of 0. 05 friction coefficient was set behind a multilayer simple reinforced concrete frame structure basement,and SAP2000 was used for modeling and analysis. It was compare the isolation situation of first layer pillars bottom made of rigid baseplate or not,and also compare the isolation situation of the structure with different isolation layer stiffness. The results show that the isolation structure having a rigid baseplate can effectively control the basement maximum slippage. The selected structure has the best isolation effect when the isolation layer stiffness is 2 000 kN / m,thus reducing the peak response of the structure in the earthquake,such as vibration period,interlayer displacement,interlayer shear and acceleration response,some damping rate even exceeds 90%.