Abstract: In order to better reveal and characterize the damage degrees and damage space forms of gassy coal rock in construction, the expression of failure approach index of gassy coal rock is deduced based on the theory of failure approach index of surrounding rock, and the uniaxial compression experiment of gassy coal rock model is carried out. Meanwhile, the three-dimensional reconstruction of uniaxial failure approach index is studied and the three-dimensional shape of the damaged space is obtained. The results show that the failure approach index of gassy coal rock quantitatively reveals the three-dimensional stress concentration degree of elastic zone and the damage degree and evolution law of damage zone. At the same time, the 3D reconstruction technology intuitively shows the damage spatial form of gas bearing coal and rock mass, which can provide a basis for the dynamic optimization of gas bearing coal and rock mass engineering design and construction scheme.