Variational mode decomposition (VMD) has been applied in the field of harmonic detection, but the error is large when the decomposition parameter K is artificially set. In order to improve the accuracy of VMD in inter-harmonic detection, first, Schmidt orthogonalization theory is used to orthogonalize the components obtained from VMD pre-decomposition in order to avoid modal aliasing. Then the residual energy corresponding to different K values is obtained, and the residual energy value minimization method is used to optimize the parameter K, and then extract the inter-harmonic signal. Finally, a symmetrical difference energy operator is used to obtain characteristic information such as the amplitude and frequency of the inter-harmonic signal. Simulation results show that the proposed method can effectively optimize the parameter K and reduce the VMD decomposition error. Compared with empirical mode decomposition (EMD), ensemble empirical mode decomposition (EEMD) and synchrosqueezing wavelet transform (SST) proposed in recent years, parameter optimized variational mode decomposition is more effective in inter-harmonic detection and has higher detection accuracy. This work is supported by the National Natural Science Foundation of China (No. 51877161).