Closed-access electrical switch may not be closed in practical application sometimes, so in order to enhance its reliability, the structure of the inertial pin and internal electrical sheet should be improved. This can be done by increasing the mass of the inertial pin, making ventilating groove on both sides of the bottom of inertial pin, changing the inertia cone angle of the head pin, decreasing the width of the support lug of the electrical sheet, so on and so forth. Through simulation and experiment, the above-mentioned measures were verified to improve the force access on the internal electrical sheet and make it deform effectively, and improve the reliability of the closed-access electrical switch.