Large-scale　wildfires　can　significantly　reduce　the　air　gap　insulation　resistance　of　high-voltage　transmission　lines　and　cause　chain　tripping　incidents.　To　assess　the　resilience　of　the　power　transmission　system　during　wildfire,　this　paper　proposes　a　resilience　assessment　framework　for　transmission　system　that　considers　the　entire　process　of　wildfire　disaster.　Firstly,　a　wildfire　spread　model,　considering　multiple　influencing　factors,　is　developed　based　on　the　cellular　automaton.　Based　on　the　air　gap　breakdown　mechanism　during　wildfires,　the　trip-out　probability　of　transmission　lines　is　calculated,　and　various　failure　scenarios　are　obtained　by　using　the　Monte　Carlo　sampling.　Secondly,　considering　the　geographical　location　of　failures,　maintenance　personnel　schedules　and　restoration　time,　a　power　transmission　system　restoration　model　is　established.　Thus,　a　resilience　assessment　method　for　power　transmission　system　during　wildfire　disasters　is　proposed.　Finally,　IEEE　RTS-79　transmission　system　is　taken　as　an　example　to　demonstrate　the　effectiveness　of　the　proposed　resilience　assessment　method.　The　results　show　that　the　proposed　method　can　effectively　calculate　the　wildfire　spread　tendency　and　transmission　line＇s　trip-out　probability.　Furthermore,　three　typical　resilience　improvement　measures　are　quantitatively　analysed,　which　provides　a　quantifiable　reference　for　the　power　sector　to　formulate　prevention　and　recovery　strategies　for　extreme　wildfire　disasters.　©　2024　The　Author(s).　IET　Generation,　Transmission　&　Distribution　published　by　John　Wiley　&　Sons　Ltd　on　behalf　of　The　Institution　of　Engineering　and　Technology.