Phenolic compounds are a class of hazardous substances for human. To study the antiradical potential of a series of phenolic compounds from the aspect of position and substituent type, phenol, o-dihydroxybenzene ( ODB ) , m-dihydroxybenzene ( MDB ) , p-dihydroxybenzene ( PDB ) , paranitrophenol ( PNP) , and o-chlorophenol ( OCP) were selected as typical targets. In addition, to elucidate the degradation discrepancy of phenolic compounds, quantum chemical calculations ( QCCs) were obtained using the B3LYP method along with a 6-311G ( d, p) basis set. Calculations indicate that phenol, ODB, MDB, and PDB, with electron-donating groups, exhibited high antiradical potential, while PNP and OCP, with electron-withdrawing groups, exhibited low antiradical potential. The chemical indices calculations show that para-compounds and ortho-compounds had high antiradical ability. Moreover, phenol, ODB, MDB, and PDB possessed higher bond dissociation enthalpy ( BDE ) and lower adiabatic ionization potential ( AIP ) values compared with those of OCP and PNP. Medium effects, even in vacuo, were also taken into account to reveal the antiradical ability of phenolic compounds.