Abstract: Orthogonal Frequency Division Multiplexing (OFDM) and single carrier digital signals are widely used in High Frequency (HF) communication. Aim at OFDM signals and single carrier digital signals have a low recognition efficiency in lower signal-to-noise ratio (SNR) and multi-path environment in HF communication, a new algorithm based on wavelet ridge is proposed. According to the wavelet ridge amplitude and wavelet ridge patterns characters can reflect instantaneous different characters of different signals types, derivation is provided of the normal used signals’ wavelet ridges characters in mathematical formula also. Corresponding to the difference between OFDM signals and single carrier digital signals in wavelet ridge amplitude and wavelet ridge patterns, differential coefficient, median filter are used in this paper, and then calculate entropy of the wavelet ridges after differential coefficient and median filter as a feature value, finally achieved to recognize of OFDM signals and single carrier digital signals. Computer simulation shows that the algorithm is not sensitive to the input signal points and this algorithm is both feasible and effective in low SNR environment.