The　classification　of　microcirculation　can　be　based　on　the　size　of　the　capillary　and　the　velocity　of　the　blood　flow.　For　each　type　of　microcirculation,　the　ad　hoc　method　is　required　to　measure　the　blood　flow　velocity.　In　this　paper,　the　correlation　method　is　used　to　measure　blood　flow　velocity　in　the　small-size　capillary.　The　large-size　capillaries　are　classified　into　three　types　based　on　the　blood　velocities,　say　low-speed,　high-speed,　and　unstable　one.　The　template-matching　algorithm,　the　Fast　Fourier　Transform　algorithm　and　a　high-speed　video　camera　measurement　are　used　to　measure　the　blood　velocities　corresponding　to　those　three　types　of　large-size　capillary.　It　was　shown　by　several　experiments　that　fairly　good　results　for　different　types　of　capillary　may　be　obtained　by　using　the　proposed　three　image　processing　algorithms.　(c)　2005　American　Association　of　Physicists　in　Medicine.