We investigated how the degradation of 7-14C-BaP aged in sediments by H2O2 treatment was influenced by the chemical structures, compositions, and microporosity of sedimentary organic carbon (SOC). Unstable OC (USOC), stable OC (STOC), mineral-protected OC (MOC), and chemically resistant OC (ROC) fractions were fractionated. The chemical structures and microporosity of the ROC fractions were characterized by 13C solid-state nuclear magnetic resonance (NMR) and CO2 adsorption technique, respectively. A first-order, two-compartment kinetics model described the degradation process very well (R2 > 0.980). The BaP degradation ratios increased with the increasing USOC contents and decreased with the increasing ROC contents. The BaP parent compound in the aqueous solution was almost completely degraded. The considerable portions of oxidized intermediates were detected in different SOC fractions, which represented either oxidized intermediates or parent compounds. The very good multivariate regressions among the degradation kinetics parameters, SOC structures and micropore volumes demonstrated that ROC-bulk, aliphatic moieties, and microporosity played crucial roles in protecting sorbed BaP from being degraded by H2O2. The results showed that ROC, aliphatic moieties, and microporosity played vital roles in Bap degradation process in sediments during H2O2 treatment, which is reported for the first time in this study.