The invention relates to an integrated gate commutated thyristor based high-power pumped storage unit starting system, and relates to the technical field of pumped storage units. The technical problems that the system structure is simplified, the harmonic content and reactive impact are reduced, and the efficiency is improved are solved. The system comprises a power grid, a synchronous motor, a static frequency conversion device, an excitation device and an on-grid switch, wherein the static frequency converter device comprises a filter, a step-up transformer, three frequency-converison-side thyristor power units and three step-down transformers, and the excitation device comprises an excitation-side transformer and an excitation-side thyristor power unit; and the armature winding of the synchronous motor is connected with the power grid through the on-grid switch, and is sequentially connected to the power grid through the static frequency converter device, a grid-side vacuum switch and a power-grid side mutual inductor, and the excitation winding of the synchronous motor is sequentially connected to the power grid through the excitation device, an excitation-side vacuum switch and an excitation-side mutual inductor. The system provided by the invention has good a torque characteristic, and can improve the on-grid success rate of the unit.