The　sorting　of　target　particles　from　heterogeneous　samples　is　challenging　yet　crucial　for　cell　biology　research　and　clinical　diagnosis.　Among　various　microfluidic　methods,　the　use　of　cavity-based　laminar　vortex　combined　with　inertial　focusing　is　a　powerful　label-free　passive　technique　for　the　selective　sorting　of　large　rare　cells　with　high　purity　and　concentration　from　billions　of　blood　cells.　However,　this　technology　faces　the　challenge　of　improving　the　cavity　holding　capacity　of　trapped　particles.　This　paper　describes　a　round　cavity-based　vortex　sorting　method　and　presents　a　novel　judgment　criterion.　The　proposed　round　cavity　achieves　a　holding　capacity　of　entrapped　target　particles　that　is　2.2-7.8　times　higher　than　that　of　rectangular　cavities.　By　comparing　the　particle　recirculating　orbits　and　the　simulated　vortex　morphology　in　round　and　rectangular　cavities,　a　mechanism　whereby　particles/cells　are　held　within　the　cavities　is　investigated.　It　is　found　that　the　area　ratios　(S　=　Ap/Ac)　of　the　particle　orbit　area　(Ap)　to　the　cavity　area　(Ac)　are　0.56　and　0.95　for　the　rectangular　and　round　cavities,　respectively.　The　results　show　that　the　round　cavity　provides　more　efficient　space　for　recirculating　particles　and　has　better　sorting　performance.　This　round　cavity-based　vortex　sorting　method　will　be　useful　for　clinical　applications.　Published　under　an　exclusive　license　by　AIP　Publishing.