The invention relates to a bi-side cam structure applied to an on-load tap-changer. The bi-side cam structure comprises an insulation rotating shaft, a cam and a positioning fastening pin, wherein the cam is fixed on the insulation rotating shaft through the positioning fastening pin, an upper mounting plate is rotatably installed on the upper end of the insulation rotating shaft, a lower mounting plate is rotatably installed on the lower end, and three vacuum arc extinguish chambers are installed between the upper mounting plate and the lower mounting plate. The structure is light and flexible, and has better calorifics and mechanical properties than a conventional cam structure. The reliability of the contact structure of an on-load switch is improved.