A better understanding of the pyrolytic characteristics of pre-oxidized lignin in which C alpha H-OH was oxidized to C-alpha=O group was obtained through four selected p-ether-type lignin-like model polymers containing the H- and G-type subunits. These models were depolymerized in closed ampoule reactor system and interrogated using in situ FTIR. The results show that their degradation products differ significantly in species and yield due to C alpha H-OH, C-alpha=O, and aryl-OCH3. The yield of phenolic monomers from oxidized G-type polymer rose to 27.87 wt%, almost twice that of initial G-type polymer. Nevertheless, as for H-type polymer, oxidation of the C alpha H-OH to C-alpha=O group lead to decreases in phenolic monomers yield by similar to half. The in-situ FTIR indicates that oxidation of the C alpha H-OH to C-alpha=O accelerates cleavage of interunit linkages and simplifies depolymerization pathways resulting in better selectivity of phenolic monomers, especially at low pyrolysis temperatures (< 500 degrees C). Several important transformation pathways are proposed that dearly explain the pyrolytic behavior of pre-oxidized polymers.