A heave compensation device of a marine operation crane comprises a hydraulic oil tank, a volume adjustable hydraulic pump, an overflow valve, a sensor, en encoder detecting movement signals of a coiling block, a controller connected with the sensor, a hydraulic control valve and a secondary component, wherein the volume adjustable hydraulic pump and the overflow valve are connected with the hydraulic oil tank, the hydraulic control valve and the secondary component are connected with the controller, and the controller is connected with the volume adjustable hydraulic pump. A load is connectedwith the coiling block and drives the secondary component to rotate, and high-pressure oil is output. The hydraulic control valve is connected with a hydraulic motor, a generator, an inverter, a proportional control valve and an energy accumulator. The secondary component is connected with the coiling block and the load, and the load is connected with the controller. The inverter is connected with a super-capacitor and the motor and exchanges information with the super-capacitor and the motor. The motor is connected with a dynamic coupling device. The controller outputs control signal to change the displacement of the volume adjustable hydraulic pump, and therefore the rotating speed of the secondary component is controlled and the compensation purpose is achieved. By means of the heave compensation device, the problems that an extra power source is needed, and the energy consumption is huge are solved, the energy utilization rate is greatly increased, and the production cost is saved.