The invention discloses an emergent switchover starting control method from water pumping to power generation of a pump storage group. Under a water pumping condition, after a guide vane is closed to the smallest opening degree and a generator switch GCB is disconnected, a rotary wheel loses the prime power in the water pumping direction, under the condition that the guide vane is not completely closed, water pressure from a pressure steel pipe forces the pump storage group to be braked and decelerated and pass through the zero rotation speed instantly, and then the pump storage group is immediately changed to be in a turbine steering direction and accelerated to the synchronous rotation speed, and grid-connected power generation is realized. The emergent switchover starting control method from water pumping to power generation of the pump storage group has the advantages that the pump storage group is stopped without inputting mechanical brake or electric brake, the work condition switchover time is effectively shortened, emergent response of a pumped storage power station when a power grid is abnormal is more effectively represented, and the safety function of the power grid is guaranteed.