Abstract: Communication countermeasure is an important component of contemporary military communications. An anti-jamming method applied in FFH/MFSK systems is introduced under a worst-case band multi-tone jamming (MTJ). Different from anti-jamming principle of combine and diversity technology, the system receiver in this method has implemented cognition and suppression of multi-tone jamming without side information based on frequency histogram and envelope detection, thereby, improving the transmission performance of system with no loss of frequency band efficiency. Further analysis and simulation indicate that the system anti-jamming performance, using this method presented in this paper, could be improved about 10 dB better than conventional combining and diversity method within correlative jamming time. The method shows both low complexity and realizability.