Aiming at the magnetic interference problem of threeaxis magnetometers in magnetic field measurement process, a new magnetic field measurement error compensation method based on damped particle swarm optimization (DPSO) algorithm is proposed. A comprehensive error compensation model for magnetometer error and geomagnetic interference field is established. DPSO algorithm and twostep method are used to carry out the parameter estimation work of nonlinear observation model, respectively. The scalar value of the proton magnetometer is taken as the true value and a nonmagnetic turntable is employed in the experiment for continuous sampling. Experiment results demonstrate that the DPSO algorithm has good suppression capability to magnetic field measurement error. After compensation, the root mean square errors (RMSE) are reduced from 1 025.7 to 60.304 4 and 581 nT for DPSO algorithm and twostep method, respectively. The results indicate that better compensation performance is achieved with DPSO algorithm, and the compensation accuracy is improved at least by one order of magnitude, which provides an efficient compensation method for magnetic field measurement error.