To improve locomotive AC drive system static and dynamic performance, and achieve accurate flux orientation with indirectfield oriented control technology implementing independent and decoupling control of torque and excitation, flux accurate orientation of vectorcontrol for Harmonic Locomotive traction motor was deducted. By using rotor q-axis flux observer model, rotor flux magnitude and positionwas analyzed, and with MRAS theory, rotor magnetic field oriented real-time correction through the adaptive adjustment was realized.Experimental results verified that the theoretical analysis was correct and the correction strategy for accurate field orientation was effective.