It is well known that a speech dialog system can be regarded as an integration of a speech interface which runs in the front end and a dialog controller which runs in the back end. The former is obviously language-dependent while the later could be language-independent relatively. This paper describes an approach to constructing a multilingual spoken dialog system. In this approach, we extended a dialog controller for Japanese to a language-independent one and combined it with a Chinese speech interface. Experimental result shows that the proposed approach is effective in constructing quickly a multilingual-supporting dialog system using a common dialog controller.