Abstract: Aiming at the problem of the waveshape distortion in the output obtained by an SR system, this paper explains the signal recovery formula from the point of view of dynamics. Taking sinusoidal signal as the research object, the motion of the particle in the bistable system and the recovery system is investigated, and the recovery mechanism and rules with and without noise are explained. Moreover, a novel explanation about pulse distortion caused by the particle’s transition is put forward and a method to recover the output signal of subthreshold SR via cascaded-bistable system and the recovery system’s parameter choice is proposed. The numerical simulation has presented that this method, which applies to the output signal directly, can recover the waveform containing weak information submerged in noise effectively.