Abstract: The collapse characteristics of roof in the goaf of steep and extra thick coal seam are different from that of gentle slope coal seam, and it is easy to form a suspended roof to induce dynamic disasters. Based on the 45° coal seam in the northern mining area of Wudong Coal Mine in Urumchi, a omprehensive three-dimensional exploration was carried out by using the ground penetrating radar to analyze the changing characteristics of the plastic zone in the roof of the goaf. The detecting results showed that the roof of the goaf did not collapse greatly with the advancement of the working face, and the suspended roof was formed. This paper proposes a scheme of cracking on roof of goaf by combining underground water injection with blasting and deep hole blasting in surface. The microseismic monitoring results show that the weakening of the roof effectively reduces the frequency of dynamic disasters caused by the sudden collapse of the roof of the goaf.