The extraction residue (ER) from a sawdust was oxidatively degraded with aqueous hydrogen peroxide (AHPO)/ acetic anhydride (AAH) under mild conditions. About 16.1% of organic matter in the ER was converted to soluble portion (SP). In total, 76 compounds were detected in the SP from the reaction mixture by two-dimensional gas chromatography/time of flight-mass spectrometry. They can be classified into 20 group components. Among them, carboxylic acids (CAs) are the most abundant, accounting for ca. 57.2%. Most of the CAs are non-aromatic ones, especially non-aromatic dicarboxylic acids. All the esters produced from the ER degradation are acetates and diacetates. The results suggest that molecular composition of macromolecular species in the sawdust is complicated and the species without highly condensed aromatic rings tend to be oxidatively degraded to soluble compounds with AHPO/AAH. In addition, CH3COO% from AAH decomposition involved in the oxidative degradation of the sawdust.