The invention discloses a hydraulic control stepless amplitude regulation device of a vibratory roller. The device comprises a box body, a fixed inner tooth ring, a planet gear I, a planet carrier, a vibration motor, an inner gear shaft, a hydraulic control gear, an amplitude regulation motor, an outer eccentric block, an inner eccentric block, a planet gear II, an inner-outer tooth ring and an outer gear shaft. According to the device disclosed by the invention, an amplitude regulation motor is driven to rotate by the pressure oil produced by a hydraulic system, the hydraulic control gear rotates synchronously, the outer gear shaft and the outer eccentric block are driven by the inner-outer tooth ring and the planet gear to rotate for corresponding angles while the angles of the inner gear shaft and the inner eccentric block are kept unchanged under the effect of the vibration motor, and then an aim of changing the angle, namely combined eccentricity, between the outer eccentric block and the inner eccentric block is achieved, so that the amplitude of the vibratory roller is changed and the stepless regulation of the amplitude of the vibratory roller is realized under the control of the hydraulic system.