Abstract: Generally, the macroscopic properties of a rock are reflected well in its micro-characteristics, so further research of microscopic properties is significant to the understanding of macroscopic properties and their practical applications in engineering. Using a lamellar casting test and a scanning electron microscope test, as well as the results of a point-loading test and a conventional mechanical test, the mineral composition and microstructure of surrounding rocks in the exploration adit of a hydropower station in southwest China was experimentally studied. The correlation between the micro-character and macro-mechanical properties of the rock was analyzed and the effects of the rock's micro-characteristics on the stability of the surrounding rock was stated from a microscopic view to establish the theoretical and technical basis for the design and construction of the tunnel support.