In hilly regions, the deep mud layer of winter paddy fields often causes rice transplanters to sink, severely compromising transplanting quality. To systematically evaluate the effects of different seedling-raising methods combined with lightweight rice transplanters on transplanting performance in such fields and explore the relationship between seeding quality and machine-transplanting quality index, this study designed experiments covering both the seedling-raising and machine-transplanting stages. During the seedling-raising phase, two methods were compared: nutrient soil and muddy soil. Three seeding rates (75, 85, and 95 g/tray) and three seedling ages (25, 33, and 40 days) were tested. In the transplanting phase, two types of lightweight equipment were used: a 4-row walk-behind transplanter and a 4-row riding high-speed transplanter. Results showed that seedling-raising method, seeding rate, and seedling age significantly affected the quality of hybrid rice seedlings. A strong correlation was observed between seedling quality and transplanting performance, particularly in deep-mud fields. Compared to the walk-behind transplanter, the riding high-speed transplanter significantly reduced the rates of missing, floating, and overturned seedlings by 0.70%-2.06%, and improved the transplanting uniformity by 2.05%. Further correlation analysis indicated that increasing plant height, leaf age, root entanglement force, and seedling fullness helped reduce missing and floating seedlings, but increased the rates of overturned and injured seedlings. Improving seedling uniformity effectively reduced floating, overturned, and injured seedlings while enhancing transplanting uniformity. Overall, the optimal combination was the riding high-speed transplanter paired with nutrient soil seedlings, a seeding rate of 85 g/tray, and a seedling age of 33 days. This configuration improved the transplanting uniformity coefficient by 0.10%-9.03% compared to other treatments, providing a practical basis for high-quality mechanized cultivation of hybrid rice in deep-mud fields.