By using the large-scale test device for coal and gas outburst simulation, the experiments of coal and gas delay outburst are conducted under the conditions of no disturbance and ball stricked disturbance of unbalanced load. The results show that delay outburst has four stages: preparation, occurrence, development and dissolution. The coal particle of outburst has size classification. The outburst coal can be divided into three parts: outburst holes, disturbed and no disturbed zone. The threshold value of delay outburst decreases and outburst possibility increases under the disturbance. The critical gas pressure has linear relation with the horizontal stress of delay outburst. The relationship between the intensity of outburst and the critical gas pressure is nonlinear. The conception of coal and gas delay outburst is redefined as the coal and gas outburst that is occurred when the main breaking coal or rocks works completed and the new mining spaces formed or when the auxiliary operation finished. The preliminary analysis of mechanics of coal and gas delay outburst is also presented.