A receptacle connector is adapted to mate with a plug connector having at least one latch. The receptacle connector includes a connector body, a plurality of terminals received in the connector body and at least one dust-proof cover. The connector body defines at least one perforation therethrough. The perforation has a first port from which the latch of the plug connector is received in the perforation, and a second port communicating with the first port. The dust-proof cover is mounted on a rear portion of the connector body to seal the second port of the perforation to prevent dust outside the perforation from entering along the perforation.