Critical　coalescence　condition　is　a　key　issue　in　designing　droplet-based　microchannel　reactors.　This　study　thoroughly　examined　the　coalescence　of　confined　long　droplets　in　T-junction　microchannel　reactors,　focusing　on　the　effects　of　stabilizer　and　asymmetry.　In　addition,　the　non-coalescence　behaviors　of　slipping　and　breakup　were　investigated.　Three　time　parameters,　including　the　film　drainage,　contact　and　breakup　times,　were　applied　to　characterize　the　coalescence,　slipping　and　breakup　behaviors,　respectively.　The　film　drainage　time　had　little　dependence　on　the　operation　conditions　in　the　case　of　stabilizer-free　coalescence,　but　was　affected　by　superficial　velocity　and　slug　length　after　the　addition　of　stabilizers.　Coalescence　required　a　greater　film　drainage　time　with　a　larger　arrival　time　difference.　The　arrival　time　difference　influenced　both　the　contact　and　breakup　times,　whereas　the　stabilizer　concentration　had　no　influence.　Models　for　these　time　parameters　were　established.　These　results　will　be　helpful　in　accurately　controlling　the　coalescence　in　T-junction　microchannel　reactors.　©　2021　Elsevier　Ltd