In　this　paper,　a　real-time　measurement　of　liquid　concentration　changing　in　a　Y-type　microfluidic　chip　by　digital　holography　is　presented.　In　the　experiments,　the　different　concentrations　of　salt　solution　are　injected　into　two　channels　of　the　Y-type　microfluidic　chip　as　a　target　object,　and　then　the　digital　holograms　related　to　the　target　solutions　are　recorded.　The　refractive　index　of　the　solution　can　be　obtained　from　the　reconstructed　phase　image.　The　experiment　results　show　that　the　real-time　changing　of　liquid　concentration　in　microfluidic　chip　can　be　effectively　measured　by　digital　holographic　microscopy.