Invarioustemperatures,theeffectsofinorganicacidsonthefreephenollevelinliquefactionproductswereinvestigated.Inthispaper,thefreephenollevelwasusedasanindicatortoevaluateliquefactionefficiency.Resultsshowedthatsulfuricacidwasthebestamongthe4acids.Undertheconditionofreactiontemperature150oC,reactiontime1.5h,liquefactionratio(liquid/particleboard)4andcontentofsulfuricacid6%,thefreephenollevelintheliquefactionproductsofwasteparticleboardis36.95%,andthatoforiginalparticleboardis24.27%.