To study the relationship between the power and energy of rock crushing in underground engineering disasters, such as rock outbursts, experiments were done on the crushing and the Protodyakonov coefficient of different rocks, the selective grinding processes classified according to particle size, and the uniaxial compressive strength. This work was based on rock crushing theory. The relationship among Protodyakonov coefficient, specific crushing energy and uniaxial compressive strength of different rocks was studied using regression analysis. The results show that the Protodyakonov coefficient of a rock is linearly dependent on rockspecific crushing energy and uniaxial compressive strength. Such a relationship corresponds to the cracking theory and can be used for further research.