The invention discloses a template attack method in allusion to SM4 cipher algorithm round output. According to the method disclosed by the invention, special channel input is taken as a premise, the SM4 algorithm round output is used as an attack point, the hamming weight or the hamming distance of the round output is selected to establish a template, and template attack in allusion to the SM4 cipher algorithm round output can be realized by a small number of templates. Meanwhile, selective input is taken as a basis in a template matching stage, a support vector machine is used to act as a tool for judgment and analysis, a bit of linear transformation output can be broken by only two times of matching, and then a round sub-key is reversely derived by inverse transformation of nonlinear transformation and linear transformation. The method disclosed by the invention effectively solves a problem that template attack in allusion to the SM4 cipher algorithm round number is infeasible at the present stage.