In　recent　years,　microfluidic　biochips　have　been　widely　applied　in　various　fields　of　human　society.　The　optimization　design　of　system　-architecture　based　on　continuous-flow　microfluidic　biochips　has　been　widely　studied.　However,　most　previous　work　was　based　on　the　traditional　chip　architecture　with　dedicated　storage,　which　not　only　limits　the　performance　of　biochips　but　also　increases　their　manufacturing　costs.　In　order　to　improve　the　execution　efficiency　and　reduce　the　manufacturing　cost,　a　distributed　channel-storage　architecture　can　be　used　to　temporarily　cache　intermediate　fluids　in　idle　flow　channels.　Under　this　architecture,　careful　consideration　of　the　volume　management　of　the　fluid　to　be　cached　is　a　prerequisite　for　ensuring　the　reliability　of　bioassay　results.　However,　the　existing　work　has　not　considered　the　volume　management　of　the　fluid　to　be　cached　in　detail.　This　may　cause　the　volume　of　the　fluid　to　not　match　the　capacity　of　the　storage　channel,　which　can　contaminate　other　fluids　and　lead　to　incorrect　bioassay　results　or　increase　the　manufacturing　cost　of　biochips　due　to　long　storage　channels.　In　this　paper,　we　propose　a　physical　design　method　for　microfluidic　biochips　that　considers　the　actual　volume　of　fluid　while　utilizing　distributed　channel　storage.　We　address　this　problem　by　taking　a　placement　and　routing　co　-design　strategy　throughout　the　iterative　process　of　the　simulated　annealing　algorithm.　Experimental　results　under　multiple　benchmarks　show　that　the　proposed　method　can　effectively　reduce　the　completion　time　of　bioassays,　minimize　the　flow　path　length,　and　decrease　the　number　of　intersections.