Abstract: In-situ geological settings of mining steeply inclined coal seams is so complex that structural characteristics of coal-rock mass is basis for dynamic control of the coal-rock deterioration.A hybrid investigation including borehole television, geological radar, digital borehole camera and DR scanning.relevant results indicate that the geological structure activity is frequent.With the borehole TV and geological radar monitoring, macro-structure of roof in mined-out area is compact and the macro-structure is quadratic stability after failure.There are abundant uncompacted hollows, which seldom affect the stability of coal-rock masses.According to the data from digital borehole camera, the coal-rock masses can be divided into triple zones including broken zone, plastic zone and elastic zone.In mesco-structure aspect being revealed by DR scanning, anisotropy of coal mass is obvious and there are a lot of original cracks and sulfur compound in the coal mass.On the contrary, the number of original cracks is bare and cementing materials like both mudstone and argillaceous sandstone reduce strength of the structure seriously, which is main causes to induce a large-scale hanging in the roof and caving.