Proliferation　is　an　important　characteristic　of　life,　and　many　signaling　pathways　participate　in　this　complicated　process.　The　MAPK/Erk　pathway　is　a　classic　pathway　in　cell　proliferation.　In　this　study,　expression　levels　of　key　factors　in　the　MAPK/Erk　pathway　were　measured　to　assess　the　proliferation　level　among　normal　skin,　physiological　scar,　and　keloid　tissue.　Thirty　patients　were　selected　randomly　from　the　Department　of　Plastic　Surgery　at　Peking　Union　Medical　College　Hospital　from　January　2019　to　December　2020.　Histological　appearance　and　fiber　tissue　content　were　observed　by　Hematoxylin　and　eosin　staining　and　Masson　staining.　Expression　levels　of　key　factors　in　the　MAPK/Erk　pathway　(ATF2,　c-Jun,　c-Myc,　p38　and　STAT1)　and　relative　proteins　(HIF-1　alpha　and　PCNA)　in　tissues　were　detected　by　immunohistochemistry　and　analyzed　as　the　percentage　of　positively　stained　cells　in　both　the　tissue　epidermis　and　dermis.　Western　blot　was　used　for　quantitative　analysis　of　the　above　factors.　In　results,　keloid　tissue　showed　a　significantly　higher　fiber　and　less　cell　content.　In　the　immunohistochemical　result,　higher　expression　of　key　factors　was　observed　in　the　epidermis　than　in　the　dermal　layer,　and　the　expression　of　all　factors　was　increased　remarkably　in　keloid　tissue.　In　western　blot　analysis,　all　factors　(except　STAT1)　showed　higher　expression　in　keloid　tissue.　In　our　former　research,　keloid　showed　similar　apoptosis　level　as　physiological　scar　and　normal　skin.　On　combining　our　former　conclusion　and　results　in　this　study,　an　imbalance　condition　between　the　high　proliferation　level　and　normal　apoptosis　level　may　lead　to　the　growth　characteristics　of　keloid.