Antibody-based　cell　isolation　using　microfluidics　finds　widespread　applications　in　disease　diagnostics　and　treatment　monitoring　at　point　of　care　(POC)　for　global　health.　However,　the　lack　of　knowledge　on　underlying　mechanisms　of　cell　capture　greatly　limits　their　developments.　To　address　this,　in　this　study,　we　developed　a　mathematical　model　using　a　direct　numerical　simulation　for　the　detachment　of　single　leukocyte　captured　on　a　functionalized　surface　in　a　rectangular　microchannel　under　different　flow　conditions.　The　captured　leukocyte　was　modeled　as　a　simple　liquid　drop　and　its　deformation　was　tracked　using　a　level　set　method.　The　kinetic　adhesion　model　was　used　to　calculate　the　adhesion　force　and　analyze　the　detachment　of　single　captured　leukocyte.　The　results　demonstrate　that　the　detachment　of　single　captured　leukocyte　was　dependent　on　both　the　magnitude　of　flow　rate　and　flow　acceleration,　while　the　latter　provides　more　significant　effects.　Pressure　gradient　was　found　to　represent　as　another　critical　factor　promoting　leukocyte　detachment　besides　shear　stress.　Cytoplasmic　viscosity　plays　a　much　more　important　role　in　the　deformation　and　detachment　of　captured　leukocyte　than　cortex　tension.　Besides,　better　deformability　(represented　as　lower　cytoplasmic　viscosity)　noteworthy　accelerates　leukocyte　detachment.　The　model　presented　here　provides　an　enabling　tool　to　clarify　the　interaction　of　target　cells　with　functional　surface　and　could　help　for　developing　more　effective　POC　devices　for　global　health.