The invention discloses an electric locking device of a subway platform screen door; an electromagnet driving mechanism is adopted to drive a ratchet synchronous wheel; a ratchet synchronous wheel component is separated from a lock fork; the lock fork rotates for a certain angle under the action of the restoring force of a torsional spring component, when a roller component is separated from the lock fork, a sliding door is opened, and when the roller component slides into the lock fork, the sliding door is closed; in order to prevent accidents, a manual unlocking device, a locking in-place detection switch component and a manual unlocking detection switch component are arranged, so as to check and make sure the electric locking or unlocking is in place, and the repair is convenient; the electric lock structure is located above the subway platform screen door, can bear the air pressure of a piston of the closed screen door and the extrusion force of passengers, has a reliable structure, is easily realized, and has good application prospect.