Apoptosis　is　a　process　of　programmed　cell　death　that　occurs　in　multicellular　organisms.　The　mitochondrial　pathway　plays　a　paramount　role　in　apoptosis.　In　this　study,　the　expression　levels　of　key　factors　in　the　mitochondrial　pathway　and　the　cell　proliferation　factor　(PCNA)　were　measured　to　evaluate　the　level　of　apoptosis　and　proliferation　in　keloid　scars,　physiological　scars　and　normal　skin　tissue.　Thirty　samples　were　taken　from　30　patients:　10　keloid　patients,　10　physiological　scar　patients　and　10　patients　without　obvious　scarring.　All　30　patients　were　selected　randomly　from　the　Department　of　Plastic　Surgery　at　Peking　Union　Medical　College　Hospital　from　June　2016　to　December　2016.　Hematoxylin　and　eosin　staining　and　Masson　staining　were　used　to　observe　the　differences　in　histology　and　fiber　tissue　content.　Mitochondrial　pathway　factors　(caspase-3,　caspase-8,　caspase-9,　Bcl-2,　Bax,　cytochrome-c)　and　PCNA　expression　levels　were　detected　by　immunohistochemistry　and　were　analyzed　as　the　percentage　of　positively　stained　cells　in　the　epidermis　and　dermis.　Relative　protein　expression　levels　were　measured　by　western　blotting.　Compared　with　physiological　scars　and　normal　skin　tissue,　keloid　tissue　had　an　increase　in　fiber　number　and　decrease　in　cell　content.　In　our　immunohistochemical　and　western　blot　analyses,　all　tissue　types　showed　similar　expression　levels　of　the　mitochondrial　pathway　factors.　However,　the　percentage　of　PCNA-positive　cells　and　the　relative　protein　expression　level　of　PCNA　were　significantly　higher　in　keloid　tissue.　Keloid　has　a　similar　apoptosis　level　as　physiological　scars　and　normal　skin　but　has　a　higher　expression　of　PCNA,　indicating　that　keloid　scars　have　high　levels　of　proliferation　and　normal　apoptosis.