Since　safety　hazards　may　occur　during　the　life　of　a　Li-ion　battery,　it　is　important　to　learn　the　behavior　under　abuse　conditions.　In　this　paper,　the　variation　of　each　characteristic　parameter　of　the　thermal　runaway　process　for　32,650,　NCM,　and　LiFePO4　square　batteries　are　analyzed　based　on　an　overcharge　experiment　in　Adiabatic　Rate　Calorimeter.　NCM　batteries　at　different　charging　rates　and　three　kinds　of　single　batteries　at　1.00　C　charging　rate　are　tested　for　exploring　the　variation　of　thermal　safety　of　lithium-ion　batteries　under　overcharge　conditions　and　getting　the　characterization　of　overcharge　battery　safety.　Furthermore,　a　new　index　overcharge　degree　is　introduced　to　evaluate　the　safety　state　of　lithium　batteries　under　different　overcharge　conditions　given　the　comprehensive　analysis　of　the　variation　trend　of　overcharged　battery　characteristic　parameters,　which　provides　ideas　for　the　early　safety　warning　of　batteries　at　overcharging　conditions.　It　is　found　that　the　initial　runaway　temperature　of　NCM　battery　decreases　gradually　with　the　increase　of　charging　rate,　but　the　initial　runaway　temperature　of　overcharge　at　2.00　C　is　slightly　lower　than　1.50　C,　the　maximum　runaway　temperature　of　battery　increases　first　and　then　decreases,　the　rate　of　voltage　rise　in　the　early　stage　increases　with　the　increase　of　charging　rate,　the　change　rate　of　voltage　and　temperature　of　the　battery　increases　as　a　whole,　the　voltage　before　thermal　runaway　decreases　first　and　then　increases,　the　total　charging　capacity　shows　a　linear　decline.　In　the　1.00　C　overcharge　experiments　of　the　three　batteries,　the　initial　runaway　temperature　of　32,650　battery　is　the　lowest,　the　maximum　runaway　temperature　of　square　lithium　iron　phosphate　battery　is　the　highest,　the　temperature　change　rate　of　square　lithium　iron　phosphate　battery　is　the　largest,　the　voltage　of　square　lithium　iron　phosphate　battery　drops　to　0　V　first,　and　the　overcharge　time　of　NCM　battery　is　the　longest.