In order to solve the problem of intrinsic torque ripple caused by nonlinear operation of interior permanent magnet synchronous motors (IPMSMs), a torque ripple suppression method based on harmonic current injection is proposed in this study. Firstly, a nonlinear IPMSM model considering magnetic saturation and harmonics in magnetic flux is established. On this basis, the coupling between harmonic torque and harmonic current is analyzed, and the Lagrangian algorithm is applied to derive an online calculation method for the harmonic reference current amplitude and phase angle. Then, the three-vector-based model predictive current control (TV-MPCC) approach is used to achieve accurate harmonic current injection and suppression of IPMSM intrinsic torque ripple. Lastly, the proposed method is verified for effectiveness in a MATLAB/Simulink simulation environment. The simulation results show that the proposed harmonic current injection control method based on TV-MPCC effectively suppressed the intrinsic torque ripple caused by IPMSM harmonic flux and cogging torque. Specifically, the IPMSM torque ripple peak-to-peak value was reduced by 63.9%, the 12th harmonic torque amplitude was reduced by 75%, and the 24th harmonic torque amplitude was reduced by 57.9% after TV-MPCC-based harmonic current injection.