Biochar can be effectively used to reduce the release of greenhouse gases and fulfill the consequences of carbon sinks. It can also be used to restore degraded soil and improve the structure of soil microbial communities and enhance their functions. This study investigated the effects of different biochar doses and the combined application of biochar with other fertilizers on soil microbial functional diversity, which would provide a scientific basis and theoretical guidance for the rational use of agricultural waste and optimal management of soil fertility in vegetable gardens. In the present study, the representative vegetable garden soil (Fimi-Orthic Anthrosols) was sampled from Lianzhou County, Qingyuan City. Pot experiments were conducted for 40 days in the laboratory. Ten treatments were performed as follows: CK (0% biochar + 0% fertilizer), T1 (0% biochar + 0.1% commercial organic manure), T2 (0.1% biochar + 0% fertilizer), T3 (0.25% biochar + 0% fertilizer), T4 (0.5% biochar + 0% fertilizer), T5 (1.0% biochar + 0% fertilizer), T6 (100(N) + 30(P₂O₅) + 75(K₂O) mg/kg oven-dried soil), T7 (0.1% biochar + 0.1% commercial organic manure), T8 (0.1% biochar + 100(N) + 0(P₂O₅) + 75(K₂O) mg/kg oven-dried soil), T9 (0.1% biochar + 100(N) + 30(P₂O₅) + 75(K₂O) mg/kg oven-dried soil), and T10 (0.1% biochar + 0.1% commercial organic manure + 100(N) + 0(P₂O₅) + 75(K₂O) mg/kg oven-dried soil), with three replicates each. Soil microbial functional diversity of the harvested soil samples was analyzed using the Biolog method. Significant variations in soil microbial functional diversity were shown in the treatments with different biochar doses. First, the T1 (0.1% organic manure) and T3 (0.25% biochar) treatments significantly increased soil microbial utilization of carbon substrates more than the other treatments (P<0.05), but further increases of biochar (>0.25%) reduced average well color development (AWCD). Second, both T1 and T3 treatments had significantly higher species richness (McIntosh index), and only the T1 treatment had higher evenness of community species (Shannon index) than the other treatments. Moreover, T1 and T3 had the highest utilization of polymers, carbohydrates, carboxylic acids, amino acids, and phenols. For the chemical fertilizer treatments, soil microbial activity and microbial utilization of carbon substrates were increased by phosphate fertilizer, but were significantly reduced by nitrogen and potassium fertilizers. Furthermore, a principal component analysis showed that there were similar soil microbial community functional structures in the treatments of T1, T2 (0.1% biochar), and T3. A single application of organic manure or biochar had stronger effects on the soil microbial community structures than the combined application; however, phosphate fertilizer and the combined application of biochar and chemical fertilizers also changed the soil microbial utilization of carbon substrates. This study indicates that it is necessary to ascertain the treatment doses of biochar and standardize their criteria to promote biochar application at large scales and in different fields. However, the biochar had some negative effects on the eco-environment. Therefore, the biochar sources and amount of biochar doses should be studied to determine the negative effects on soil, to prevent these in future treatments for optimal results.