The invention discloses a WEB terminal controlled message middleware system and a data transmission method thereof. The data transmission method comprises the steps of: S1, initializing a WEB terminal controlled message middleware system; S2, according to client setting, utilizing the WEB terminal controlled message middleware system to receive data from a sending client in a pushing or pulling mode, and convert the data into a JSON format message; S3, according to receiving client setting, utilizing the WEB terminal controlled message middleware system to convert the message required by a corresponding client into a format designated by a corresponding receiving client, and employing a pushing or pulling mode to send data to the corresponding receiving client. The technical scheme can realize data exchange among heterogeneous systems and different data storage formats in a company or among companies.