The invention discloses a method for disconnecting a lead of a bus isolation switch. The method comprises the steps of arranging an insulation platform below a bus which lead disconnection operation of the isolation switch is needed; rising the insulation platform to an operation position right below the bus; performing equipotential lead disconnection operation of the isolation switch at the operation position right below the bus on the insulation platform. By the method, an operator does not need to enter phases for operation, and the lead disconnection operation of the bus isolation switch is safely and efficiently achieved.