In　this　paper,　we　present　a　novel　optical　microfluidic　cytometry　scheme　for　label-free　detection　of　cells　that　is　based　on　the　self-mixing　interferometry　(SMI)　technique.　This　device　enables　simple,　fast　and　accurate　detection　of　the　individual　cell　characteristics　and　efficient　cell　type　classification.　We　also　propose　a　novel　parameter　to　classify　the　cell　or　particle　size.　Artificial　polystyrene　beads　and　human　living　cells　were　measured　using　this　system,　and　the　SMI　signal　properties　were　statistically　evaluated.　The　capability　of　the　proposed　cytometer　for　cell　type　discrimination　and　size　classification　has　been　validated　by　the　measurement　results.　Our　study　can　provide　a　very　simple　technique　for　cell　enumeration　and　classification　without　any　extra　devices　such　as　high-speed　camera,　photomultiplier　and　spectrometer.　Moreover,　the　fluorescence　staining　operation　which　is　necessary　in　traditional　flow　cytometry　methods　is　not　required　either　in　our　system.