Abstract: A new experimental method, taking expansive agent as loading way, is presented based on features of coal and outburst features. When expansive agent is put into limited space, its volume can expand after hydration reaction. The pressures because of expansion can reach to more than 50 MPa to ambient medium, and its increasing process is a typical dynamic character. The reason caused coal and gas outburst is that elastic strain energy stored in coal seam originally releases suddenly when the condition of stress is changed. The physical process of coal and gas outburst is simulated in the test through expansive agent dynamic loading. The results indicates that the test method of dynamic loading of expansive agent in limited space can truly simulate the coal stress and boundary conditions of outburst. So it may be a good test method to research the problems of coal and gas outburst.