The current spectrum analysis method of Loran-C signals based on Fourier transform method, which can not realize the real-time monitoring of the signal spectrum. The Short-Time Fourier Transform (STFT) method is used to model and simulate Loran-C signals under different signal-to-interference ratio, sky wave amplitude and delay conditions, and the time-frequency database of the signal is established. The STFT analysis of Loran-C signal and spectral peak comparison with time-frequency database can effectively solve the problem of sky wave identification and sky wave delay measurement with high real-time requirements.