The invention relates to a socket connector, a plug connector, and a connector formed by combining the socket connector with the plug connector for an electric water heater, as well as the electric water heater which is provided with the plug connector and the socket connector. A movable isolating cover is mounted in the socket connector, can seal an insertion hole corresponding to a charged contact in a shell body, and can be pushed only by a pushing insertion hole. A pushing insertion rod which can be inserted into the pushing insertion hole is arranged on the plug connector, thereby pushing the isolating cover, so as to open the insertion hole corresponding to the charged contact. The structure is safer and more reliable, and can prevent electric shock due to mis-touch, thereby greatlyimproving the safety of the socket connector.