A string light assembly includes a string light connector and a lighting module electrically connected with the string light connector. The string light connector includes a cable, a plug connected with one end of the cable, and a socket module connected with the other end of the cable. The socket module has a plurality of interface modules of which at least one is used for connecting the lighting module, and at least one is used for connecting a plug of another string light connector. A plurality of the string light assemblies are connected to form a light string by engaging the plugs and the corresponding interface modules of the socket modules thereof with one of the plugs used for connecting to a power source. The string light assembly is designed to facilitate the connection and disconnection between two string light assemblies so as to conveniently adjust the length of the light string.