Thermal　failure　propagation　is　one　of　the　most　severe　challenges　for　battery　modules　and　it　usually　aggravates　the　thermal　hazards,　further　resulting　in　serious　accidents.　This　work　conducted　two　groups　of　experiments　to　investigate　the　influence　of　discharging　treatment　and　module　shape　on　the　thermal　failure　propagation　of　battery　modules,　where　the　triangle　module,　rectangle　module,　parallelogram　module,　line　module,　hexagon　module,　and　square　module　were　researched.　Based　on　the　results,　it　can　be　found　that　an　evident　domino　effect　existed　on　the　thermal　failure　propagation　of　battery　modules.　Namely,　the　failure　propagation　process　consisted　of　several　phases　and　the　number　of　phases　depended　on　the　shape　of　the　module.　Besides,　it　is　indicated　that　discharging　treatment　on　a　battery　module　when　it　was　in　a　high-temperature　environment　would　aggravate　its　thermal　failure　propagation　by　bringing　an　earlier　thermal　failure,　a　quicker　failure　propagation,　and　a　larger　mass　loss.　Combining　the　results　of　safety　and　space　utilization,　it　is　revealed　that　the　triangular　module　may　be　the　best　choice　of　battery　module　due　to　its　smaller　failure　propagation　speed　and　higher　space　utilization.　©　2018　by　the　authors.