The invention discloses a connection method of a back-to-back starting device of a pumped storage power station. The method comprises steps that 1, a mechanical press bus between an electric generatorcircuit breaker of the mechanical press of the electric generator and a phase changing isolation switch is leaded to a connection starting loop branch and is connected with a wire connection terminalof a first starting isolation switch and the transformer side terminal of the phase changing isolation switch is electrically connected with a low-voltage side wire connection terminal of a main transformer; 2, the connection starting loop branch of the mechanical press bus between the electric generator and the electric generator circuit breaker is connected with a wire connection terminal of asecond starting isolation switch; 3, an electric generator braking switch used for stopping of a unit is connected between the second starting isolation switch and the electric generator circuit breaker; and 4, after the outgoing terminal of the first starting isolation switch and the outgoing terminal of the second starting isolation switch are electrically connected and then leaded to a sharingstarting bus. The method is advantageous in that any one unit is used as the prime power starting unit, and other units can be started, so the operation mode of the motor unit is flexible.