This study aims to further understand the effect of carbon structure on the physiochemical status of metals and thus its activity during volatile-char interactions. The chars with distinctly different carbon substrates prepared from the pyrolysis of pine sawdust at 400 and 1000 °C were impregnated by different Fe contents, which were used as catalysts for benzyl phenyl ether (BPE, a typical lignin dimer) decomposition. The results demonstrated that the conversion of BPE was prominently improved with the iron addition, especially when the char prepared at the high temperature was loaded with 10% and 20% iron. The difference in carbon structure of two original chars have clearly resulted in the co-existence of various FexOy in chars at 400 °C and the dominant presence of α-Fe2O3 in chars at 1000 °C. Together with the Fe-containing active sites, the high orientation of carbon structure in the char from 1000 °C has considerably favored the high selectivity of product formation during the catalytic reforming of BPE and its derived volatile components.