Micromechanical properties of the shale play a key role in the drilling，completion，and fracturing of reservoirs.In this paper，the marine shale in Sichuan Basin and continental shale in Shiguai Basin of Inner Mongolia were studied by XRD，SEM，and indentation test. The results show that marine shale in Sichuan Basin is mainly composed of authigenic minerals such as quartz，calcite，dolomite，and pyrite，while continental shale is composed of exogenous minerals such as quartz，kaolinite，montmorillonite，and albite. The microscopic structure of marine shale is relatively compact，while the continental shale develops intergranular pores and the structure is relatively loose. The indentation test results show that the average Vickers hardness（Hv）of marine shale is above 2.43 kN/mm2；the rock stiffness is hard and stiff，and the breakdown pressure required for the reservoir is high. The average Hv of continental shale is 0.80 kN/mm2；the rock is relatively weak，and the breakdown pressure of the reservoir is low. Marine shale has a large indentation displacement difference in different directions and is prone to radiation fractures，indicating that the rock brittleness is significant. Continental shale has similar indentation displacement in different directions and is not prone to radiation fractures，indicating that the rock brittleness is relatively weak. Combined with the energy theory，low net fracture pressure is adopted in marine shale reservoir fracturing to reduce the fracture rebound in the later period，while high net fracture pressure can be considered in continental shale reservoir fracturing to ensure fracture residual width.