The invention discloses a construction method of a rock structural plane damage statistical constitutive model considering a size effect, which comprises the following steps of: firstly, simplifying astructural plane into an equivalent thin layer, and determining damage variables according to the number of damaged mesoscopic microelements and the total number of the mesoscopic microelements in the thin layer; secondly, obtaining a damage probability density function of the mesoscopic unit body; then, determining a reasonable damage initial stage, simulating the structural plane load condition, and obtaining a statistical damage constitutive model of the structural plane under the shearing effect; secondly, according to stress balance in the shearing process, determining the relation amongnominal shearing stress, effective shearing stress borne by the undamaged infinitesimal body and shearing stress borne by the damaged infinitesimal body, and obtaining a damage evolution model and astructural surface shearing deformation damage constitutive model of the structural surface in the shearing deformation process; determining parameters m and u0 of the structural plane shear deformation damage constitutive model, and establishing a structural plane shear constitutive model considering the size effect based on the nonlinear relationship between the parameters and the size; finallyverifying the correctness.