Recently,　as　microfluidic　devices　have　been　widely　used　in　the　chemistry,　life　science,　lab-on-a-chip,　micro　electro　mechanical　systems(MEMS)　and　so　on,　the　characterization　of　fluid　behavior　at　the　scales　of　micro　and　nanometer　levels　is　essential.　Because　of　the　small　scales　and　low　Reynolds　numbers,　surface　forces　become　important　relatively.　The　flow　behavior　in　micro-scale　is　significantly　different　from　that　in　macro-scale　and　many　complex　phenomena　are　not　clear.　Micro-scale　particle　image　velocimetry　is　a　kind　of　full　field,　instantaneous　and　quantitative　method　that　can　be　used　to　characterize　the　performance　of　such　microfluidic　system　with　spatial　resolutions　better　than　one　micron.　It　has　been　an　important　measurement　technique　and　been　widely　studied.　In　this　article,　the　recent　development　of　Micro-PIV　including　the　fundamentals　the　technique　and　the　theoretical　background　is　reviewed.　An　overview　of　the　most　relevant　applications　is　given　on　the　topics　of　near-wall　flow,　electrokinetic　flow,　mixing,　biological　application,　bubble　flow　and　so　on,　and　its　progress　is　forecasted.　©　2012　Journal　of　Mechanical　Engineering.