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In order to solve the problem that the existing driven pulping machine has too much power consumption, seriously damages the soil structure and lets the straw float under the condition of returning the straw to the field in the northeast rice area, an undriven soil puddling machine with improved automatic-leveling and strawburying functions was designed for paddy rice field. The machine consisted of a rack, a star rake group, a rolling roll, a leveling device and a flat device. The star rake in the front can finely crush the soil and bury the straw, and the rolling in the back can further finely crush the soil and press bury the straw. The flat device can level the surface, and the electro-hydraulic control system can automatically level the ground, which can create excellent plot conditions for rice transplanting operation. Through theoretical analysis and optimization design, the structural parameters and arrangement of the star-shaped rake were determined. The rolling roller was equipped with tooth plate and cutter tooth, and the tooth plate with inclined arrangement and the cutter tooth with upright were used to cut the soil laterally and longitudinally respectively, which can improve the effect of burying straw in fine soil. The flat floor was improved and the height of the flat floor was determined to be 150mm. Simulation tests were carried out on the forward speed, plate width and pushing angle. The optimal working parameters of the flat floor were obtained as follows: forward speed was 2.4km/h, plate width was 290mm and pushing angle was 44°. Electronic hydraulic control system of automatic leveling based on inclination sensor and PID algorithm was designed by using the center stationary leveling strategy, which realized the fast and stable control of the automatic leveling system. Filed experimental results showed that the surface flatness of the whole machine after operation was 0.73cm, the straw coverage rate was 91.4%, the stubble depth was 5.98cm, and the slush degree was 1.18g/cm3. The indicators of the machine and tools were better than the national standards. The design can provide a reference for the research of the water ground preparation machine and tools under the condition of full straw returning to the field in northeast rice region.