Flow　regimes　of　two　immiscible　liquids　at　the　cross　junction　within　a　rectangular　microchannel　are　experimentally　investigated.　Characteristics　of　the　flow　regimes　including　critical　conditions　and　interfacial　deformations　are　presented.　It　is　found　that　the　occurrence　of　the　tubing　regime　is　favored　by　increased　viscosity　of　the　dispersed　phase　or　reduced　cross-sectional　aspect　ratio,　leading　to　the　shrinkage　of　the　flow　rate　range　that　could　produce　droplets.　In　order　to　reveal　the　physical　mechanism,　the　force　analysis　is　carried　out　based　on　the　tunnel　structure　formed　between　the　interface　and　channel　side　walls　within　the　rectangular　cross-section.　The　reshaping　stage　and　pinch-off　stage　are　mainly　driven　by　the　interfacial　tension,　leading　to　far　larger　neck　thinning　rate　compared　to　the　superficial　velocity　of　either　phase.　The　filling　stage　and　squeezing　stage　are　dominated　by　the　pressure　drop　across　the　dispersed　tip　while　the　role　of　the　shear　force　becomes　more　important　with　increasing　tunnel　width.　The　filling　period　is　estimated　as　t(2)approximate　to　kHw(n0)(2)/Q(d)　with　k　=　1.34　and　the　squeezing　period　is　expressed　as　t(3)/T-c　=　0.3Ca(c)(-1).　According　to　the　force　analysis,　the　critical　tip　velocity　under　dripping　scales　with　three　key　parameters,　which　can　be　expressed　as　(u(tip)/U)*　similar　to　Q(c)L(tip)/w(tunnel)(3).