Aiming　at　complex　industrial　processes,　a　method　considering　the　influence　of　operation　mode　and　equipment　standby　for　evaluating　the　voltage　sag　tolerance　characteristics　of　industrial　processes　is　proposed,　which　takes　the　PIT(Parameter　Immunity　Time)　as　the　voltage　sag　tolerance　index.　The　connectivity　of　nodes　under　current　operation　mode　is　analyzed,　and　the　impact　range　is　analyzed　with　the　occurrence　point　of　voltage　sag.　Then　the　original　process　fault　tree　is　established　and　corrected　according　to　the　judgment　result　of　the　disturbed　equipment.　The　whole　process　PIT　is　calculated　by　using　PIT　of　a　single　device　to　evaluate　the　whole　process　voltage　sag　tolerance　characteristics.　The　production　process　of　an　actual　TFT-LCD(Thin　Film　Transistor　Liquid　Crystal　Display)　is　analyzed　and　the　analytical　results　prove　the　correctness　and　feasibility　of　the　proposed　method.　©　2019,　Electric　Power　Automation　Equipment　Press.　All　right　reserved.