Abstract: Based on the gas and coal outburst mechanism, the process and its dynamic sources of gas and coal delay outburst in uncovering coal seam in cross-cut are analyzed; the effect of ground stress and gas pressure on delay outburst, energy change relation and dynamic source formation process are expatiated. From the accidents causes and theoretical analysis, it shows that the delay outburst is not only related with the intensity and length of stress-relaxation zone and stress concentration zone, but also with the gas pressure and stress peak; the dynamic sources includes the coal seam ground stress, gas pressure, gas internal energy, external force and coals' physical-mechanical properties. The formation process of dynamic sources is complex and polytropic, the gas and ground stress are the main energy, therefore, decreasing gas pressure, gas internal energy and ground stress are the basic way to reduce the delay outburst. The results can offer theoretical and technological support for fast uncovering coal seam in cross-cut.