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In the process of rice growth, the weeds will decrease the quality and yield of rice. At present, both herbicide and manual weed control have many shortages. Chemical weed control causes environmental pollution, reduces crop nutrition and increases weed drug resistance. Manual weed control is laborintensive, lowefficient and bounds labor. Mechanical weed control is helpful to protect environment and the high efficient will be an irresistible trend. In order to improve the weeding rate and reduce the damage rate of rice seedlings while weeding, the mechanism analysis and improvement of paddy field weeding device was were done. The weeding device was symmetrically installed on the two groups of spring tooth disc (left and right). The two groups of spring tooth disc rotated to complete the weeding by flexible shaft. According to kinematics analysis of the key components of spring tooth disc and the strength analysis of rice seedlings and barnyard grass, the kinematics model of spring tooth disc and stress model of paddy rice seedlings and barnyard grass were established. According to the stress analysis, the strength condition of rice seedlings and barnyard grass were presented. According to physical characteristics of rice seedlings and barnyard grass and the basic parameters of spring tooth disc, the variation range of rotating angular velocity and teeth number of spring tooth disc were obtained. Through various testing on the compaction device, the optimum working parameters of the compaction device were obtained. The test showed that rotating angular velocity was 25.1rad/s and teeth number was 5. Performance testing in field was carried out for the paddy weeding device. The results showed that weeding rate was 80% and injury rate was 4.5%. The weeding machine had good quality, and had met the agronomic technical requirements when rotating angular velocity was 25.1rad/s and teeth number was 5.