Electromagnetic force simulation of isolation knife switch was done by simulation software. The phase angle difference of three phases was 120°, current amplitude was applied in one of three phases respectively for three times simulation. The electromagnetic force of number 4 contact finger of middle phase was tensile force without conductive bridge model, and that of number 4, number 10, number 16 and number 22 contact finger of middle phase was tensile force with conductive bridge model, when the current amplitude was applied in left phase. The electromagnetic force of all contact fingers was compression force, when the current amplitude was applied in middle phase. The electromagnetic force of number 3 contact finger of middle phase was tensile force without conductive bridge model, and that of number 3, number 9, number 15 and number 21 contact finger of middle phase was tensile force with conductive bridge model, when the current amplitude was applied in right phase. The value of tensile force of middle phase contact finger was about 1N without conductive bridge model. The value of tensile force of middle phase contact finger was 10.41N ∼ 16.61N with conductive bridge model. The maximum value of current density appeared in contact positions of contact fingers.