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A 1PJ-4.0 laser leveler installed on a wheeled tractor through the hydraulically driven 3-point linkage is developed. The harrow of the laser leveler can move up and move down by a cylinder and a planar four bar linkage. Hydraulic systems of the laser leveler are designed, including height position control hydraulic system, leveling control hydraulic system and folding hydraulic system. Experiments are carried out to investigate the dynamic response characteristics of the height position control system and leveling control system, respectively. The response time of leveling harrow moving up is almost twice as much as moving down. The moving up velocity of leveling harrow increases with the rate of accelerator pedal deepness, while the moving down velocity of leveling harrow is stable because a one-way throttle valve has been applied in the height position control hydraulic system. The average moving up time is about 3.31~4.23s and the move down time is 1.7s in testing space of 400mm. It is bilateral symmetry of rotate angular velocity in the clockwise and reverse to control plow leveling. The results of the paddy field experiment show that the laser leveler installed on wheeled tractor for paddy field can work steadily, and the surface smoothness of paddy field can be obviously improved. The maximum height variation of paddy field surface decreases from 32cm before leveling work to 4.9cm, and the relative standard deviation reduces from 12.28cm to 2.64cm. The cumulative percentage of the sampling points, which have smaller than or equal to 3cm of absolute difference value, is more than 69.4%.