Because of the high aspect ratio and large upper mass of electrical equipment with multi-column posts in substation or converter station, large overturning moment is generated under earthquake action. Conventional isolation devices can not bear the tensile force caused by the electrical equipment with multi-column posts under earthquake action, so there is a lack of research on the application of isolation devices in electrical equipment with multi-column posts. The finite element models of capacitor bank tower with multi-column posts and its isolation structure are established. The stress of capacitor bank tower under three-dimensional El Centro earthquake is analyzed, and the effect of tensile isolation device on reducing the peak stress of capacitor tower post is studied. The analysis results show that before and after the application of the isolation device, the peak stress of the post insulator of the capacitor tower is 15.11 MPa and 6.48 MPa, respectively. The isolation efficiency is 57.1%.