Disclosed is a language conversion system and a service method thereof, capable of allowing a user to easily obtain foreign language translation data while using a messenger by operating a skin for a messenger application helper in combination with the messenger based on window message information of the messenger without accessing a messenger server The language conversion system provides a language conversion service to a plurality of terminal equipments connected to an Internet network and includes a server module and a DB server. The server module provides a messenger application controller, which forms the skin for the messenger application helper at one side of the messenger activated in the terminal equipment, to the terminal equipment, receives information value, which is selected and changed by the user, from the messenger and the skin for the messenger application helper and requests data corresponding to the information value to the DB server The server module transfers the data output ted from the DB server to the skin for the messenger application helper. The DB server extracts foreign language data approximate to the data inputted into the server module by the user from a corpus database and transfers the foreign language data to the skin for the messenger application helper The user is able to make real-Lime communication with foreigners through the messenger by utilizing the language conversion service without separately displaying an electronic dictionary or a translation program on a window screen.