In　the　case　of　fluid　flow　with　a　low　Reynolds　number,　the　internal　fluid　stratification　can　be　easily　observed　after　droplet　coalescence,　impeding　rapid　mixing　of　fluid.　In　this　study,　the　capillary　pressure　difference　is　increased　by　adjusting　the　droplet　size　and　the　interfacial　tension,　so　that　a　strong　jet　can　be　generated,　resulting　in　a　rapid　mixing.　Five　distinct　droplet　mixing　modes　have　been　found.　The　phase　diagram　of　the　droplet　mixing　modes　is　obtained　and　the　transition　rule　of　the　droplet　mixing　modes　is　established　on　this　basis.　A　novel　energy　distribution　model　is　employed　to　analyze　the　dependence　between　liquid　bridge　expansion　and　jet　movement　of　two　droplets.　In　addition,　a　criterion　for　evaluating　the　mixing　efficiency　of　droplets　is　presented.　The　results　presented　in　this　paper　provide　a　theoretical　basis　and　practical　guidance　for　realizing　the　efficient　mixing　of　microfluids.　©　2021　Elsevier　Ltd