Method and system for expanding Web application (App) functions

The invention provides a method and a system for expanding Web App functions. The method includes that a function expansion field comprising an expansion JS function and serving as an address of a local application responding to expansion JS function requirements is added in the Web App; function parameters are sent to a browser kernel by calling the expansion JS function; a Web App frame sets the address of a local application program into the address of the local application responding to the expansion JS function requirements according to calling messages received by the browser kernel; a target application program designated by the address is activated according to the address of the local application; and the activated target application program executes the expansion JS function according to the parameters of the expansion JS function and sends the execution results back to the Web App. According to the method and the system for expanding Web App application functions, the Web App can use functions of other applications installed on the operation system directly to expand functions of the Web App.