The invention provides a protection device for series compensation equipment. A thyristor bypass switch, a spark gap and a bypass switch are bridged between the winding ends of a series transformer; after a fault occurs, before the bypass switch is switched on, and when the series compensation equipment is in an overvoltage state, the thyristor bypass switch is turned on, or the spark gap reachesa fixed value and acts, the windings of the series transformer are bypassed, and therefore, overvoltage protection can be performed for the series compensation equipment. The thyristor bypass switch,the spark gap and the bypass switch of the protection system cooperate with one another so as to realize coordinated protection for the overvoltage of the equipment, prevent the further development ofthe stress of the overvoltage and improve the overall reliability of the equipment.