The invention provides a method for evaluating brittleness of a shale reservoir and belongs to the technical field of nonconventional oil and gas reservoir evaluation. The method comprises the following steps: acquiring an elastic parameter and a brittleness mineral parameter of the shale reservoir to be evaluated, wherein the elastic parameter comprises Young modulus*density; carrying out cross analysis on the Young modulus*density and other elastic parameters and/or the brittleness mineral parameter and according to a cross analysis result, determining a value domain of the Young modulus*density; according to p-wave and s-wave impedances obtained by prestack inversion, establishing a Young modulus*density attribute volume; evaluating the brittleness of the shale reservoir to be evaluated by the Young modulus*density attribute volume in the value domain. According to the invention, accuracy of evaluating the brittleness of the shale reservoir is improved, prediction on planar distribution of the brittleness in the integral research region is implemented and the method has wide application prospect in the field of exploration and development of shale gas.