Abstract: Salvia miltiorrhiza is a significant medicinal crop in China. The quality of its transplantation directly impacts root development, the accumulation of effective medicinal components, and the final yield. In Shaanxi Province, the one-ridge-three-row staggered planting pattern is widely practiced due to its advantages in soil-moisture conservation and improved field ventilation. However, transplanting operations under this configuration remain predominantly manual, resulting in high labor intensity, low efficiency, and difficulty in maintaining uniform planting quality. Existing transplanting machinery suffers from several limitations, including poor compatibility between machine structure and staggered agronomic configuration, unstable seedling posture during insertion, oversized machine dimensions that reduce field maneuverability, and insufficient adjustability of planting depth. These constraints hinder the mechanization of Salvia miltiorrhiza cultivation and limit improvements in planting uniformity and production efficiency. To address the specific mechanization requirements of this crop in Shaanxi Province, a micro self-propelled transplanter suitable for one-ridge-three-row staggered planting was designed and developed. The proposed machine consists of a lightweight frame, a rotary staggered seedling-feeding mechanism, a large-stroke eccentric-wheel-cam-linkage planting mechanism, a walking mechanism, and a compact transmission system. To accommodate the spatial characteristics of the staggered three-row configuration, a rotary feeding structure was developed to deliver seedlings continuously in a coordinated and phase-matched manner. Based on agronomic requirements for deep insertion, stable anchoring, and upright seedling posture, together with the biomechanical properties of Salvia miltiorrhiza seedlings, a large-stroke planting mechanism incorporating an eccentric-wheel-cam-linkage system was designed. This mechanism provides extended vertical displacement, an optimized insertion angle, and smooth kinematic performance to reduce lateral disturbance during soil entry and enhance seedling uprightness after transplanting. A complete kinematic model of the planting mechanism was established to evaluate and optimize its mechanical behavior. Optimization objectives were defined from the perspectives of planting stability, insertion-angle control, vertical-depth accuracy, and adequacy of planting stroke. A parameter optimization framework of multi-objective genetic algorithm is constructed. The optimal combination of member dimensions is determined using MATLAB App Designer. Fifteen structural parameters, including critical linkage lengths and pivot coordinates, were selected for optimization. Sensitivity analysis identified L₁, L₂, L₄, L₆, and L₇ as the most influential parameters affecting planting stroke and seedling uprightness.After optimization, the mechanism achieved a theoretical planting stroke of 324 mm, providing sufficient vertical motion for deep insertion. The minimum insertion depth reached 191.44 mm, meeting agronomic requirements for effective seedling anchorage. Furthermore, the mechanism guarantees near-vertical soil penetration, which significantly enhances the verticality of the plug seedlings and minimizes disturbance from lateral displacement.These improvements ensured that the optimized mechanism satisfied agronomic requirements for deep, upright, and stable planting. A prototype micro self-propelled transplanter was fabricated based on the optimized parameters and tested under typical field conditions in Shaanxi Province. With a theoretical plant spacing of 304 mm and an average seedling length of approximately 150 mm, the field results showed a qualified planting rate of 94.75%, indicating high operational reliability. The coefficient of variation of plant spacing was 8.71%, demonstrating acceptable planting uniformity for medicinal-crop production. The planting-depth qualification rate reached 89.90%, confirming effective depth control during operation. Seedlings exhibited high uprightness and stable anchorage after transplanting, further validating the effectiveness of the optimized mechanism. Overall, the developed micro self-propelled transplanter effectively addresses the major shortcomings of existing equipment by integrating a rotary staggered feeding mechanism with an optimized large-stroke planting mechanism. Its validated field performance demonstrates that it meets the core agronomic requirements for Salvia miltiorrhiza cultivation and provides an efficient and reliable solution for mechanized transplanting in Shaanxi Province and similar production regions. This work offers theoretical and technical support for specialized transplanting equipment for medicinal crops and contributes to the advancement of precision mechanized planting technology in China.