In this paper, we simply introduced the traditional decision support system and its characteristics and limitations. And then some new types of intelligent decision support system are recommended, such as GDSS, DDSS, 3IDSS and IDSSKD. And at last IDSS based on natural language understanding are described in detail. Some techniques and methods of IDSSNLU are introduced detailedly. The prospects of IDSS based on natural language understanding is put foreword.