Due to the harmonic caused by the nonlinear load, the error of electric power measurement still exist in power system at present. To settle the problem, a new kind of measurement mode based on partial least-squares regression method is presented in this paper. The model of electric system and the model of harmonic meter have been completed by MATLAB. Utilizing the signals of harmonic voltage and harmonic current measured synchronously at PCC, regression coefficients are worked out through partial least-squares algorithm. After that, the supply harmonic impedance is gained, consequently the harmonic voltage source of system and the harmonic current source of the load can be calculated correctly. So the harmonic meter can measure the direction and amplitude exactly. The new model can distinguish harmonic power which comes from the linear load, nonlinear load and system. The irrational problem of measurement model has been solved. The simulation analysis and the analytic result of practical engineering road-testing data indicate that the proposed method is valid and feasible.