Abstract: To explore the effects of biochar and functional microbial agents (Bacillus megaterium) on the fertility of urban garden soil and the growth of Bougainvillea, this study took Bougainvillea, a typical urban road green plant in Guangzhou, as the research object and conducted a pot experiment. Five treatments were set up: T₁ (adding 0.0235 g/kg fish protein fertilizer), T₂ (adding 1% camphor tree biochar), T₃ (adding 0.5 g/kg functional microbial agent), T₄ (adding 1% camphor tree biochar + 0.5 g/kg functional microbial agent, and T₅ (adding 1% camphor tree biochar + 0.5 g/kg functional microbial agent) + 0.0235 g/ kg fish protein fertilizer), with no treatment as the blank control (CK). The results showed that in terms of Bougainvillea growth, all treatments could advance the flowering period of Bougainvillea, significantly increase the number of flowers, increase the height and ground diameter of Bougainvillea by 48.40% and 23.24% respectively compared to the control group at the 90th day of cultivation, significantly increase the total nitrogen and total phosphorus content in the Bougainvillea root system, and improve the root morphology. In terms of the physical and chemical properties of soil, compared with CK, all treatments could effectively improve soil quality. Among them, the T₄ treatment significantly increased the soil pH value, electrical conductivity, organic matter, dissolved organic carbon, total phosphorus, total potassium, alkali-hydrolyzable nitrogen and available potassium content by 24.9%, 316.0%, 663.7%, 371.2%, 123.2%, 67.6%, 89.8% and 246.2% respectively, with the most significant improvement effect. The T₅ treatment significantly increased the soil urease and neutral phosphatase activity by 355.6% and 93.5% respectively, while the T₄ treatment significantly increased the soil amylase and neutral protease activity by 92.4% and 94.0% respectively. High-throughput sequencing results showed that the Chao1 and Shannon index increased, indicating that fish protein fertilizer, biochar and functional microbial agents all made the soil bacterial community structure more diverse and balanced, with the T₄ treatment group having the largest proportion of OTUs. In conclusion, the combined application of biochar and functional microbial agents has the best effect on the improvement of garden soil, and the addition of fish protein fertilizer (0.0235 g/kg) on this basis can promote the growth of Bougainvillea and significantly increase the number of flowers.