Abstract: As the volume of urban garden waste continues to grow, aerobic composting has become a key approach for its utilization as a resource. However, existing composting models face challenges such as low fermentation efficiency and poor maturation. Research on specialized and efficient microbial agents tailored for garden waste in South China remains insufficient.To screen efficient fermentation microbial agents suitable for garden waste composting, this study used garden waste from Guangzhou as raw material and established four treatment groups: a blank control (CK), traditional old material inoculation (A1), addition of compound microbial agent 1 (Bacillus amyloliquefaciens and Bacillus licheniformis, A2), and addition of compound microbial agent 2 (Bacillus subtilis, Saccharomyces cerevisiae, and Aspergillus niger, A3). A composting experiment was conducted to monitor the dynamic changes in temperature, pH, electrical conductivity (EC), and germination index (GI). The mature compost was then used to formulate cultivation substrates for a Salvia farinacea Benth. cultivation trial. The results showed that the A3 treatment initiated composting most rapidly, reaching a maximum temperature of 75°C, with a high-temperature phase (≥60°C) lasting 52 days. At the end of composting, the A3 treatment exhibited optimal overall performance, with a pH of 8.23, EC of 1.42 mS/cm, and GI of 98.7%. The substrate formulated from the A3 compost product (T3) demonstrated the best performance in the cultivation of Salvia farinacea Benth. ‘Yichuanlan’, with plant height, crown width, tiller number, fresh and dry weight of the plant significantly higher than those of the control group, and the SPAD value increased by 22.0% compared to CK. These findings indicate that the addition of compound microbial agent 2 can significantly enhance composting efficiency, improve the quality of mature compost, and increase the agricultural value of the product, providing practical technical support for the efficient resource utilization of garden waste.