A　novel　synthetic　technology　of　p-nitrobenzoic　acid　has　been　investigated　with　dioxygen　by　using　metalloporphyrins　RTPP-(MCl)-Cl-III　(M　=　Fe,　Co,　Mn)　as　biomimetic　catalysts.　Oxidation　of　p-nitrotoluene　to　p-nitrobenzoic　acid　under　2.0　MPa　of　O-2　in　the　presence　of　a　microamount　of　metalloporphyrins　(RTPP-(MCl)-Cl-III)　at　55　degrees　C　was　achieved　with　the　highest　(　up　to　90.4%)　yield.　Further　research　results　show　that　the　catalytic　activities　were　relative　to　the　nature　of　the　substituted　groups　and　the　central　metal　ions　of　metalloporphyrins.　For　the　metalloporphyrins　with　the　same　center　metal　ions,　the　greater　the　electron-withdrawing　degree　of　groups　in　the　porphyrin　ring,　the　higher　the　catalytic　activities　of　the　metalloporphyrins.　The　catalytic　activities　for　metalloporphyrins　with　different　center　metal　ions　followed　the　order　RTPPMn　Cl-III　＞　RTPP　(FeCl)-Cl-III　＞　RTPP　(CoCl)-Cl-III.