A locomotive power measurement method based on the combination of fast Fourier transform and wavelet transform is presented for electric locomotives complex operating environment in which lots of non-steady-state harmonics are difficult to be measured accurately. First, wavelet transform is applied to find out the signal point mutation and to determine whether the given calculation cycle signal is steady or non-steady. Next, the steady signal is analyzed by FFT, while the non-steady signal is analyzed by wavelet method. Finally, the energy value of each frequency component in signal is calculated by phasor algorithm. Simulation results show that the algorithm can accurately measure the harmonic power.