Soil organic matter (SOM) plays a vital role in regulating metal bioavailability. However, the relationship of SOM and its fractions, including water soluble substance (WSS), fulvic acid (FA), humic acid (HA), and soil microbial biomass (SMB), with metal bioavailability to plants has not yet been thoroughly investigated. A pot experiment was carried out to explore effects of exogenous humic acid on soil organic carbon (SOC)，its composition and soil microbial biomass (SMB) in rhizosphere and bulk soils, 6 months after its application, and correlation analysis done of carbon content in each fraction of the soil SOC with Pb content in various parts of the tea plant. The experiment, using yellow-red soil collected from Fuyang, was designed to have three levels of HA application rate (0, 300 and 600 mg kg^-1 DW) and two levels of Pb concentration (0 and 300 mg kg^-1), making up a total of 6 treatments. After the pots, 3 kg of air-dried yellow red soil each, were amended separately with Pb, they were left for aging for 30 days. Then each pot had four uniform seedlings transplanted in. After successful transplantation, three levels (0, 300, and 600 mg kg^-1 DW) of HA were amended separately with irrigation. Six months later, the plants were harvested separately by new leaf, old leaf, new shoot, old shoot and root, for analysis of Pb concentrations in these tissues of the plants. SOC, WSS, FA, HA and SMB in the rhizosphere and bulk soils in the pots were extracted and quantified using a Multi N/C Total Organic Carbon Analyzer. Results show that in the pots that had not been spiked with Pb, the rhizospheric soil was lower than the bulk soil in SOC, whereas in the pots that had, a reverse trend was observed. Amendment of HA significantly increased SOC and SMB both in the rhizospheric and bulk soils, but the effect was affected by Pb spiking. High concentration of HA significantly increased FA in the rhizosphere soil, which was probably attributed to degradation of some of the HA amended. No significant relationship was found between the various fractions of SOC in the bulk soil and Pb concentration in the tea plants, and neither was observed of the SOC and HA in the rhizosphere soil with Pb concentration in various tissues of the plants. However, Pb concentrations in young and old leaves, young and old shoots and roots, were found to be all significantly or extreme significantly and positively related to WSS and FA in the rhizospheric soil, and significantly but negatively related to SMB therein. After all, application of HA in soil changes contents of SOC and its fractions and in turn bioavailability of Pb to and its distribution in the tea plant.