Abstract: Abstract: For rice seedling transplanting, there are more than 5 kinds of planting patterns in China, including equal row carpet seedling transplanting, wide-narrow row carpet transplanting, equal row pot seedling transplanting, wide-narrow row pot seedling transplanting, and semi-pot seedling transplanting. The zigzag wide-narrow row rice seedlings transplanting is a new method of planting adjacent rows of rice seedling alternately, and distributing wide and narrow rows. This kind of planting method absorbs the merits of traditional equal row pot seedling planting, wide-narrow row carpet seedling planting and zigzag planting. The pattern of zigzag and wide-narrow row pot seedling transplanting can increase the light penetration and ventilation of the paddy-field, which brings some advantages such as reducing the plant diseases and insect pests, increasing lodging resistance ability of rice and improving the rice yield and quality for rice production. In this paper, a variable and differential transplanting mechanism for zigzag wide-narrow row rice pot seedlings was presented. This mechanism consists of 2 major parts that are transmission case and gear case. There are 10 gears, including 2 pairs of noncircular gears, 2 pairs of bevel gears as well as one pair of spur gears, employed to transform one input constant rotational speed into 2 output rotational speeds which are used to drive the noncircular gear case. Based on the non-uniform and spatial transmission of differential gear train, this mechanism can achieve a special figure-eight spatial-shaped trajectory, which can meet the kinematic requirements of zigzag wide-narrow row pot seedling transplanting. In order to obtain closed, smooth and continuous pitch curves, non-uniform B-spline curve was applied to fit the pitch curve of non-circular gear, and the mathematical model of gear train in gear case was established based on coordinate transformation theory. Moreover, the trajectory and attitude requirements of the zigzag wide-narrow row pot seedling transplanting were parameterized into 9 specific kinematics optimization objectives. Based on the development platform of MATLAB, an optimization program was compiled to analyze the effect of transmission case noncircular gear pitch curve and gear case noncircular gear pitch curve on the shape of trajectory. Further, the effects of the structure and position parameters of the gears and transplanting arm on the target parameters of the transplanting trajectory were analyzed. By human-machine interaction, a group of structural parameters including data points of pitch curves meeting the requirements were optimized. Using these parameters, a 3D (three-dimensional) model of the mechanism was built, and virtual simulation was carried out. The optimizing value: the offset of seeding section is 3.9 mm, the track length of valid seeding is section is 45.6 mm, the height of the transplanting mechanism is 32.6 mm, the distance between the teeth of non-circular gear and large-ring buckle grafting trajectory is 6.7 mm. The simulation trajectory and velocity data of the transplanting arm clip were basically consistent with theoretical results. The parts of the right transplanting mechanism were processed and assembled. The trajectory and attitude of transplanting arm were analyzed by test bench, industrial camera and image processing software. The results were consistent with the theoretical data, which verified the feasibility of the transplanting mechanism and the rationality of the structure.