Abstract: Giddens believes that modernity is a kind of institutional modernity supported by a series of institution. And then,he argues modern risk is a kind of man-made institutional risk in essence. Abstract system inherent in modern institution is the kernel of modern institution and it mainly includes two dimensions consisted of symbol systems and expert systems. So,the abstract system also becomes the core concept of modernity and its consequences that Giddens understands and analyses.Based on this,the paper tries to discuss the essence of modern risk from the crisis of symbol systems and expert systems,to understand the Giddens' institutional risk theory more fully and accurately and provide the relevant reference for the construction and perfection of our country's institution.