To　better　understand　the　physical　mechanism　of　leukocyte　separation　via　microfluidics,　a　level　set　method　was　employed　to　analyze　the　coupled　deformation-flow　of　individual　leukocytes　in　microfluidic　parabolic　shear　blood　flow.　The　results　show　that:　(1)　Weber　number　and　viscosity　ratio　have　great　effects　on　the　deformation　of　single　leukocyte,　(2)　difference　between　the　deformation　and　motion　behavior　of　different　subtypes　of　leukocytes　(i.e.,　granulocytes,　lymphocytes,　monocytes)　was　observed,　and　(3)　the　existence　of　a　second　leukocyte　significantly　changes　the　leukocyte　deformation　and　motion.　These　results　shed　light　on　the　understanding　of　the　motion　and　deformation　of　leukocytes　in　microchannel　flow　and　provide　a　theoretical　foundation　for　separating　lymphocytes　via　microfluidics.