The invention discloses a mineral content-based brittleness evaluation method for a shale gas reservoir. By taking the brittleness of quartz as the standard, the relative brittleness degree, called as a mineral brittleness coefficient, of each essential mineral in the shale gas reservoir is determined; the essential minerals comprise the quartz, clay-contained quartz, kaolinite, Mexico clay, mixed clay, calcite, dolomite, rock salt, kerogen, perthite, anorthose, feldspar, anhydrite, zeolite and natrolite; the overall brittleness degree of reservoir rock is computed by utilizing mineral volume content and the brittleness coefficient of each mineral; the mineral volume content refers to the percentage that the volume of minerals in porous rock accounts for the total volume of the porous rock. The brittleness evaluation method is superior to a method, used in oil exploration industry at present, for evaluating brittleness by comparing the volume content of the quartz and carbonatite and the total volume of the minerals.