Abstract: The method of ISAR imaging and echo modeling based on modulated step frequency waveform was studied. After the key problem of modulated step frequency signal processing was anatomized, the continuously moving multi point target modeling was given, and furthermore, a new ISAR imaging method of modulated step frequency waveform was put forward. The simulation results of target imaging under different speeds were obtained from a multi point target echo modeling, which proved the validity of ISAR imaging of this waveform.