Background:　Idiopathic　orbital　inflammatory　pseudotumor　(IOIP)　is　a　commom　orbital　disease,　with　serious　eye　symptoms　and　replase　tendency,　and　its　pathogenesis　is　still　unclear.　Nuclear　factor-κB　(NF-κB)-related　proteins　participate　in　many　important　pathophysiological　process,　however,　whether　NF-κB　plays　a　role　in　the　IOIP　process　is　worthy　of　attention.　Objective:　This　study　was　to　explore　the　roles　of　NF-κB　pathway　in　IOIP　pathogenesis.　Methods:　Twenty-four　IOIP　specimens　were　collected　during　surgery　in　Beijing　Tongren　Hospital　from　September　2010　to　May　2016.　The　histopathological　characteristics　of　IOIP　were　examined　by　hematoxylin　and　eosin　staining.　The　expression　and　location　of　NF-κB/p65,　p-p65,　p50　and　inhibitor　of　κB　(IκB-α)　were　detected　by　immunohistochemistry　and　verified　by　immunocytochemistry　and　Western　blot　assay.　Results:　The　histopathological　features　of　IOIP　were　numerous　small　lymphocyte　infiltraion　and　fibrous　tissue　proliferation,　and　a　lot　of　epithelioid　cells　were　seen　in　lacrimal　gland-involved　specimens.　NF-κB/p65　was　positively　expressed　in　the　cytoplasm　of　all　24　specimens　and　the　nucleus　in　15　specimens　with　the　expressing　rate　of　62.5%.　p50　was　expressed　in　the　cytoplasm　in　22　specimens　with　the　expressing　rate　of　91.7%　and　in　the　nucleus　in　17　specimens　with　the　expressing　rate　of　70.8%.　The　positive　expression　of　p-p65　was　found　in　22　specimens　with　the　expressing　rate　of　91.7%,　and　IκB-α　was　expressed　in　the　cytoplasm　of　11　specimens　with　the　expressing　rate　of　45.8%.　These　results　were　confirmed　by　immunocytochemistry　and　Western　blot　assay.　Conclusions:　NF-κB　pathway　is　activiated　during　IOIP　process,　and　NF-κB　pathway　may　be　involved　in　the　pathogenesis　of　IOIP.　Copyright　©　2017　by　the　Chinese　Medical　Association.