The invention provides an agricultural machinery damping device based on magnetorheological fluid. The agricultural machinery damping device comprises a cylinder body, a bottom plate, a piston rotating shaft, and a piston plate, wherein the cylinder body is provided with a sleeve, the bottom plate is installed on the cylinder body in sealed and matched modes, the piston rotating shaft is arrangedin the sleeve in penetrating and threaded connection modes, and the piston plate is located in the cylinder body, and rotatably connected with the piston rotating shaft, the magnetorheological fluid,a first coil and a second coil are arranged between the piston plate and the bottom plate, a through hole is formed in the piston plate, a displacement sensor for controlling the two coils is arrangedon the piston plate, a supporting cover for transmitting vibration and a third spring for damping are arranged at the upper end of the piston rotating shaft, a first supporting rod is arranged at thetop end of the interior of the cylinder body, and a first spring for damping sleeves the first supporting rod, second supporting columns are arranged on the bottom plate, and second springs for damping sleeve the second supporting columns. According to the agricultural machinery damping device based on the magnetorheological fluid, through elastic force of the springs at each level, thread friction between the piston rotating shaft and the sleeve, electromagnetic induction repulsion between the two coils and the change of the state of the magnetorheological fluid, resistance is generated to suppress vibration, a variety of force are mutually combined and act jointly, and thus an agricultural machine works smoothly.