Aiming at the problem of time-consuming calculation due to a large number of numerical calculation models used in the back analysis of geomechanical parameters in complex underground engineering, a new bionic optimization surrogate back analysis method (HBA-GPR-FLAC^3D) is proposed. The method takes the error between the numerical calculation results of the surrounding rock and the measured value as the optimization objective function, and the geomechanical parameters as the optimization variables. The HBA with excellent optimization performance is used to search for the global minimum value of the objective function. In the local optimization of the current optimal operator neighborhood, the GPR surrogate model is used as the operator fitness evaluation tool instead of the objective function constructed based on FLAC^3D calculation. The research shows that compared with the back analysis method based on the bionic optimization algorithm, the number of numerical model calls of the proposed method is significantly reduced under the condition of the same calculation accuracy. It is suitable for rock mechanics parameters of complex underground engineering whose single-time numerical calculation is relatively time-consuming.