According to the idea of FFT（Fast Fourier Transform）→ optimization window → IFFT（Inverse Fast Fourier Transform）， the performance constraints of window function integration in linear time-frequency transformation are broken through， achieve the application of high-performance optimization window function in linear time-frequency transformation is achieved， and establish a new time-frequency transformation algorithm， K-S transformation is establisged. After frequency shifting for the FFT spectrum vector of signal x（t） is carried out， Hadamard multiplication with the spectrum vector of Kaiser optimization window at the frequency shift point， and then inverse FFT transformation （IFFT） on the product result is performed， the K-S transform complex time-frequency matrix is constructed to obtain three-dimensional time-frequency amplitude and time-frequency phase information of x（t）. The mathematical derivation， local properties， linear properties， and variable resolution properties of inverse transformation are given； simulation experiments on steady state and time-varying superharmonic signals from 0~150 kHz power grids show that the K-S transform has better resolution in both time and frequency domains than popular short-time Fourier transform and S-transform， and has excellent variable resolution performance. The actual measurement of 0~40 kHz superharmonic signals proves that the absolute error of superharmonic voltage amplitude measurement based on K-S transformation is less than 0.032 3 V.