Abstract: In order to determine the structure and damage of the roof rock mass,we combine the pulse EKKO PRO geological radar and the borehole peep to determine the distribution law of the roof cracks,which make full use of complementary advantages of geological radar and the borehole peep,which provides a reliable theoretical basis for the design of roadway roof support.Borehole peep can reflect the discontinuity surface of the roof rock mass(such as bedding,joints,cracks),but the maximum drilling depth is only 4m because of site condition.The accurate detection range of geological radar is 0-10m,so it can be extended to the place where the borehole peep cannot reach,but it cannot accurately describe the fracture of surrounding rock.The results show:we can see that the structural abnormalities area is distributed in the range of 3.5m and 6.3m from the geological radar waveform.We know that the rock near the wall hole of 3.5m is serious damaged from the borehole peep image.So we can determine there is roof separation.Thus,it is feasible to detect the structure and failure of the roof rock mass by using the geological radar.The combination of two methods can not only judge the scope of surrounding rock fracture in macroscopic,but also observe the breaking situation of the surrounding rock and the direction of fracture form the micro level