Abstract: Manual handling of plug seedling has significantly confined the mechanized planting in previous semi-automatic transplanting machines. It is necessary to update the current complex control system with high labor intensity and low work efficiency. In this study, a mechanically- driven system with automatic picking and throwing for plug seedling was developed, combining the latest transplanting mode of plug seedling and agronomic requirements in Xinjiang Region, China. Two devices were designed, including the tray feeding device as well as the mechanical seedlings taking and throwing device. The new system was mainly composed of power transmission subsystem, tray feeding, mechanical seedlings taking/throwing, and conveying device. The horizontal and vertical seedling driving mechanism was used for the tray feeding device to drive the plug for the automatic feeding and taking of 128-hole plug seedlings. The driven power was from the ground wheel. Moreover, the mechanical transmission was realized through the deflection/picking cam driving mechanism and the manipulator. The trajectory and posture of the manipulator were set in the “Z”-shaped plug feeding plan for taking and throwing seedlings. The dimensional relationship of the deflection/taking driving mechanism was determined for the mechanical seedlings taking and throwing device. A kinematics model was constructed for the driving device in the mechanical seedling taking and feeding mechanism. The main parameters were analyzed, including the end displacement, velocity, acceleration of manipulator, and motion equations of deflection and extraction drive device. SolidWorks software was used to simulate the trajectory and motion of the seedling, in order to verify the performance of the system. The transplanting objects were selected as the pepper plug seedlings with a 60-day seedling age and a substrate moisture content of 24.61% to 31.57%. A displacement reliability test of hole-plate feeding and an experiment indoor were carried out to determine the main technical parameters, and thereby to evaluate the indicators of performance. The standard of “dry land planting machinery” was used to describe the planting performance of clamp- and hanging-cup type transplanter. Test results showed that the motion track of the manipulator reached the design requirements, where the deviation was less than 1 mm for the simulated distance between the longitudinal and transverse displacements of hole-plate feeding, compared with the theoretical value. The seedlings taking and throwing system realized various actions, according to the design requirements. There was a significant impact of seedlings taking rate on the success rate in the range of 64-88 plants/min. Specifically, the success rate of seedlings taking and throwing increased first and then decreased, with the increase of seedlings taking rate. The total success rate of seedlings taking and throwing first increase and then decrease, and the overall success rate of seedling transplantation fluctuated slightly. The best performance was achieved at the taking rate of 80 plants/min, where the average values of the total success rate of seedlings taking and throwing, the success rate seedlings takign, the success rate of seedlings throwing, and the success rate of seedling transplantation were 92.54%, 92.93%, 99.57%, and 100.00%, respectively. The dispersion degree of each success rate index was small, and there was no damage to the seedlings during the process. In addition, the indicators were in agreement with the specified values of planting performance in the mechanical industry standard. The planting frequency and qualification rate were 80 plants/min and higher than 90%, respectively. The missed taking rate and seedling damage rate were lower than 5%. These results further demonstrated that the developed system met the demands of automatic feeding of plug seedlings, taking and throwing seedlings, as well as seedling delivery before planting pepper plug seedlings with a hole height of 45 mm, together with the feasibility and reliability of the access system. The findings can provide a potential reference to design the follow-up mechanical automatic plug transplanter.