In order to extract and detect the Frequency Hopping(FH) signals in communication confrontation under fixed-frequency interference, a method based on local adaptive threshold is proposed.On the basis of Short Time Fourier Transform (STFT), a suitable local adaptive threshold value is obtained to eliminate the effects of fixed-frequency interference and to extract the frequency hopping signals.Furthermore, the signals can be detected by using the difference between the signals and Gaussian noise on continuity.Simulation results show that this algorithm can detect the frequency hopping signals effectively with low computational complexity and high reliability when the Interference to Signal Ratio（ISR） is 10 dB whether there is frequency collision (The hopping signal has the same frequency as the interference frequency) or not.