Abstract: The mechanism of coal and gas outburst is too complicated to model through conventional analytical approaches, and dimensional analysis is an effective method to study this kind of problem. The nature and controlling parameters of coal and gas outburst problem were analyzed by using dimensional analysis method. The results show that there are three main physical phenomena in the process of coal and gas outburst, which are the instability of quasi static-rock mass system, the continuous breakage of coal mass around outburst cavity, and the movement of two-phase flow with coal fragment and gas. The nature, modeling method and state variables of these 3 phenomena are discussed respectively. On this basis, a series of dimensionless numbers controlling coal and gas outburst are constructed by using dimensional analysis method. The main influence factors of coal and gas outburst are derived from these dimensionless numbers, and the coupling influences of these influencing factors on the occurrence law of coal and gas outburst are also explained.