The　frequent　accidents　of　power　lithium-ion　battery　have　become　the　major　reason　to　hinder　the　development　of　electric　vehicles.　In　this　paper,　the　thermal　runaway　process　for　a　32650　battery　is　analyzed　based　on　300　degrees　C　oven　heating　experiment　in　adiabatic　rate　calorimeter,　the　rise　of　temperature,　the　drop　of　voltage　and　the　leakage　of　electrolyte　are　observed　before　exploding,　which　could　be　used　as　predictor　variables　for　thermal　runaway　warning.　A　large　number　of　smoke　releases　and　diffuses　after　explosion,　which　could　be　utilized　as　a　criterion　for　determining　the　explosion.　And　a　lumped　chemical　reaction　kinetics　model　coupled　with　three-dimensional　heat　transfer　model　is　constructed　for　further　discussion.　The　thermal　runaway　process　of　the　battery　could　be　accurately　calculated　by　the　coupled　model.　Thermal　radiation　plays　a　more　important　role　in　heat　transfer　than　heat　convection　in　the　process　of　thermal　runaway.　The　explosion　happens　when　the　temperature　achieves　around　230　degrees　C,　and　the　active　material　mainly　starts　to　decompose　at　this　moment.