The invention discloses a speed measurement device for a pump storage group static frequency converter and a speed measurement method thereof. The speed measurement device comprises a controller, and a photoelectric encoder and a fluted disc probe which are respectively connected with the controller. The photoelectric encoder is connected with the main shaft of a pump storage group through a coupler. The fluted disc probe is aligned with a main shaft fluted disc which is installed on the main shaft of the pump storage group. The photoelectric encoder and the fluted disc probe are used for detecting rotating speed of the pump storage group so as to acquire encoder pulse signals and probe pulse signals and transmit the encoder pulse signals and the probe pulse signals to the controller. The controller performs frequency judgment on the received encoder pulse signals and the probe pulse signals and obtains the judgment result to act as group rotating speed output pulse signals to be transmitted to the speed feedback control end of the static frequency converter of the pump storage group. The problem of failure of dragging caused by signal jittering of the photoelectric encoder under the condition of high-rotating-speed dragging of the group can be solved so that safe and reliable and economic and practical dragging work of the pump storage group with stable signals and great protection can be realized.