Predicting　the　critical　transition　condition　for　different　behaviors　of　droplet　flowing　through　a　micro　contraction　is　a　classic　academic　issue,　and　there　is　currently　a　lack　of　a　simple　and　universally　applicable　prediction　formula.　This　article　aims　to　construct　critical　transition　conditions　for　different　droplet　behaviors　through　their　char-acteristic　time.　In　present　work,　the　droplet　behavior,　including　deformation　and　breakup,　are　observed　in　a　locally　contractive　microchannel　by　a　high-speed　camera.　By　tracing　the　dynamic　evolution　of　droplet　interface,　it　is　found　that　the　essential　differences　between　droplet　deformation　and　breakup　is　whether　the　minimum　neck　width　will　be　less　than　the　critical　value　for　the　appearance　of　the　irreversible　collapse.　Based　on　this,　two　characteristic　times　are　proposed　to　describe　the　deformation　and　breakup　processes,　which　well　explain　the　trend　of　flow　pattern　transition　lines.　Two　mathematical　models　are　established　for　the　two　characteristic　times,　and　the　critical　conditions　for　the　transformation　from　deformation　to　breakup　is　derived　from　these　models.　The　predicted　results　are　in　good　agreement　with　the　experimental　results,　indicating　the　applicability　of　the　pro-posed　method　in　this　paper.