Nine　chloro-iron　tetraphenylporphyrin　(RTPPFeCl)　compounds　were　designed　and　synthesized,　and　their　catalytic　activities　were　characterized　by　using　dioxygen　liquid-phase　oxidation　of　p-nitrotoluene　(PNT)　to　p-nitrobenzoic　acid　(PNBA)　as　model　reaction,　and　their　molecular　frontier　orbital　energies　EHOMO,　ELUMO,　ΔEL-H　etc　were　calculated　by　using　the　PM3　semi-empirical　molecular　orbital　method.　The　QSAR　(quantitative　relationship　between　structure　and　catalytic　activity)　of　chloro-iron　tetraphenylporphyrin　(RTPPFeCl)　was　investigated　by　combining　activity　(yield　of　PNBA)　with　EHOMO　and　ΔEL-H　of　9　catalysts.　It　was　found　that　there　was　excellent　linear　correlation　between　catalytic　activity　and　frontier　orbital　energy.　Through　linear　regression　the　following　equations　were　obtained:　that　is,　for　T　(o-R)　PPFeCl,　Y　=　71.766-8.166EHOMO-10.701ΔEL-H,　and　correlation　coefficient　R　=　0.964.　For　T(p-R)　PPFeCl　:　Y　=　80.031-9.297EHOMO-14.288ΔEL-H,　and　correlation　coefficient　R　=　0.998.　It　was　also　concluded　that　the　effect　of　EHOMO　on　catalytic　activity　was　larger　than　that　of　ΔEL-H　for　5-coordinate　of　iron　porphyrins.　EHOMO　was　the　main　structure　parameter　influencing　catalytic　activities　of　5-coordinate　of　iron-porphyrin　compounds.　Moreover　the　catalytic　activities　of　two　iromporphyrin　compounds　with　substituted　methyl　group　were　predicted　according　to　this　relationship.　The　results　showed　that　the　catalytic　activity　of　metalloporphyrin　was　consistent　with　that　predicted.　The　results　made　it　possible　to　use　the　model　of　structure-activity　relationship　to　predict　unknown　catalysts.　Finally,　the　same　correlation　between　the　catalytic　activities　and　electronic　structure　parameters　of　the　Co,　Mn　and　Fe　metal　porphyrins　were　obtained　according　to　the　authors＇　research　work　published　in　three　papers.　These　results　will　help　not　only　to　enrich　biomimetic　catalytic　theory,　but　also　to　design　excellent　biomimetic　catalysts　from　molecular　levels.