The　thermal　failure　propagation　is　one　of　the　most　severe　challenges　for　battery　pack　and　it　usually　aggravates　the　thermal　hazards,　further　resulting　in　serious　accidents.　A　series　of　thermal　failure　researches　were　conducted　to　explore　the　effects　of　state　of　charge　(SOC),　the　number　of　heaters,　failure　location　and　pack　size　on　the　thermal　failure　propagation　of　battery　pack.　According　to　the　results,　it　is　found　that　there　exists　an　obvious　domino　effect　in　the　thermal　failure　propagation　of　battery　pack.　Typically,　the　thermal　failure　of　battery　pack　can　be　divided　into　several　phases.　The　higher　SOC　worsens　the　propagation　of　battery　pack.　Besides,　the　thermal　failure　appears　earlier　for　the　pack　with　larger　number　of　heaters.　If　the　battery　close　to　the　center　of　pack　takes　thermal　failure,　the　failure　propagation　will　be　aggravated.　Moreover,　it　is　exhibited　that　the　thermal　failure　propagation　will　be　delayed　longer　when　failure　propagates　to　the　outermost　layer　of　batteries　with　the　increase　of　pack　size.　(C)　2018　The　Electrochemical　Society.