Abstract: To address the pressing need for fully automated cabbage transplanting and to tackle the issues of low efficiency and high damage rates associated with existing seedling picking device, this study developed a horizontal constant-orientation rotary high-speed low-damage seedling picking device. First, in order to optimize the device, a stem compression test was conducted to select the optimal cushioning material for the seedling picking end, which aimed to minimize mechanical damage during the seedling picking process. In addition, a stem bending test was carried out to establish a theoretical basis for determining the appropriate clamping speed range of the seedling picking actuator. Furthermore, a feasibility test on stem-clamping-based seedling picking was performed, which verified the feasibility of using the clamping method for seedling picking.Second, based on the aforementioned tests,a horizontal constant-orientation rotary high-speed low-damage seedling picking device was designed. This device comprises multiple whole-row seedling picking and disturbution modules, each equipped with servo motor-based individual modules, and employs a horizontal constant-orientation rotary seedling delivery mechanism. This design effectively minimizes stem bending damage that may occur due to posture changes during the delivery of plug seedlings, thereby facilitating whole-row seedling picking and ensuring slow evenly spaced seedling disturbution. By optimizing various factors influencing mechanical damage during the seedling picking process, this device further mitigates mechanical injury to plug seedlings, ultimately achieving high-speed and low-damage seedling retrieval through low-frequency rotation of the whole-row seedling picking and disturbution modules.To further enhance the performance of the seedling picking device, this study analyzed and calculated key parameters related to critical components including the seedling picking end effector, a multi-stage scissor-type seedling distribution mechanism, a structural diagram of the horizontal orientation mechanism, and limit side plates. Additionally, a test bench control system was developed comprising both a "stepper motor control system" and a "servo motor control system". Finally, the experiment selected 128-cell plug seedlings of the cabbage variety "Zhonggan 11" as the test subjects. The experimental factors included seedling picking frequency, servo motor rotation time, and servo motor rotation angle. The evaluation indicators comprised seedling picking success rate and respiration intensity of the damaged pot-plate seedling. A response surface experimental design based on Box-Behnken Design (BBD) was employed for this study. Through variance analysis, response surface analysis, and multi-objective optimization, a bench test investigation into the seedling picking performance of the whole-row seedling picking and disturbution modules was conducted. This resulted in an optimal parameter combination: a seedling picking frequency of 56 seedlings/min, a servo motor rotation time of 437.97 ms, and a rotation angle of 83°. Validation tests performed on the bench demonstrated that under these optimal parameters, the average seedling picking success rate achieved by the device was 96.30%, while the respiration intensity of the damaged pot-plate seedling measured at 4.40‰; these values exhibited errors of only 0.82% and 0.20‰ respectively when compared to predictions from regression models. Compared to existing cabbage seedling picking devices, the proposed multi-body constant-orientation rotary device exhibited stable improvements in success rates and effective control of mechanical damage.The research findings indicate that this approach offers a novel solution for designing seedling picking devices intended for fully automated cabbage transplanters while also providing an innovative method for assessing seedling picking damage.