The invention discloses an amplitude modulation excitation mechanism and an amplitude modulation component, and the amplitude modulation excitation mechanism comprises a vibration shaft, an amplitude modulation component and a fixed eccentric block, wherein the amplitude modulation component comprises a movable block sheathed on the vibration shaft, a sliding block positioned in a cavity of the movable block and a spring providing reset force for the sliding block, and the cavity of the movable block is set to allow the sliding block to slide to the direction which is far away from the vibration shaft when the vibration shaft rotates; and the fixed eccentric block is positioned on two sides of the amplitude modulation mechanism and rotates synchronously with the vibration shaft, the fixedeccentric block comprises a first eccentric part and a second eccentric part, which are symmetrically distributed about the vibration shaft, and one of the first eccentric part and the second eccentric part is selected to rotate synchronously with the amplitude modulation component. The amplitude modulation excitation mechanism has simple structure, an additional power device is not required for amplitude switching, the eccentricity of the excitation mechanism of a road roller can be gradually increased during the start oscillation process, and the start oscillation pressure of a hydraulic system can be obviously reduced.