Compound　droplets　have　wide　applications　in　various　fields　such　as　chemical　engineering,　medicine,　and　biological　detection.　The　size　and　shell　thickness　are　the　key　characteristic　parameters　in　the　application　of　compound　droplets,　and　studying　the　dynamic　characteristics　of　compound　droplets　is　of　great　significance　for　establishing　corresponding　manipulation　methods,　which　is　helpful　to　further　realize　the　on-demand　production　of　compound　droplets.　In　this　study,　Y-shaped　and　T-shaped　bifurcation　structures　were　prepared　using　microfluidic　technology　to　investigate　the　flow　behaviors　of　double　emulsion　droplets　(referred　to　as　double　emulsion　droplets)　at　the　bifurcation　structures.　Based　on　the　number　of　the　inner　and　outer　droplet　breakups,　the　flow　patterns　were　categorized　into　three　types:　twice　breakup,　once　breakup,　and　non-breakup.　The　transition　law　of　flow　patterns　and　the　influence　of　droplet　length　on　the　transition　of　flow　patterns　were　analyzed.　The　evolution　processes　of　characteristic　parameters　such　as　the　inner　and　outer　droplet　extension　length,　neck　width,　and　gap　width　were　discussed　to　elucidate　the　corresponding　dynamic　characteristic,　the　droplet　movement　processes　were　divided　into　three　stages:　squeeze,　transition　and　recovering　in　the　non-breakup　mode,　and　squeeze,　transition　and　fracture　in　the　once　breakup　and　twice　breakup　modes.　It　was　found　that　an　increase　in　droplet　length　effectively　reduces　the　gap　width　between　the　droplet　and　the　channel,　leading　to　increased　squeezing　and　shearing　forces　on　the　double　emulsion　droplet,　promoting　droplet　splitting.　Based　on　well-established　single　emulsion　droplet　theories,　critical　splitting　conditions　for　inner　and　outer　droplets　were　separately　formulated,　the　splitting　critical　line　of　T-shaped　bifurcation　structure　was　higher　than　that　of　the　Y-shaped　bifurcation　structure.　Furthermore,　the　capillary　number　and　initial　length　of　inner　and　outer　droplets　were　identified　to　determine　the　distribution　of　flow　patterns,　and　a　flow　pattern　map　was　constructed,　effectively　delineating　different　pattern　regions.　It　has　important　reference　value　for　regulating　the　characteristic　parameters　of　double　emulsion　droplets.　©　2024　Chinese　Society　of　Theoretical　and　Applied　Mechanics.　All　rights　reserved.