The invention proposes a capacitor fastening device. The capacitor fastening device comprises a capacitor installation plate and capacitor fixing equipment, wherein the capacitor installation plate is used for installing a capacitor, the capacitor fastening device comprises a base and a bolt, the base is fixed on the capacitor installation plate, a threaded hole and a through hole are arranged in the base, communicate with each other and penetrate through the base, the bolt comprises a screw head, a screw rod and a threaded part, the screw head and the threaded part are respectively arranged at two ends of the screw rod, and the length of the through hole is larger than the length of the threaded part. In the capacitor fastening device provided by the invention, the base is directly welded and fixed on the capacitor installation plate, thus, the bolt cannot be separated from the base in a loosen state by the threaded hole part of the base, the threaded part of the bolt can be automatically aligned to a fixing hole in the fixing equipment, a handle is prevented from extending to an installation position for alignment, fastening, installation and disassembly can be performed on an external end surface of the capacitor, and a space required for installation is reduced.