Fluid flow behavior in nanoscale channels of great importance to reveal the mechanism of nanofluidic systems and helps design of lab-on-chip devices. The measurement of fluid behavior in nanochannels is one of the fundamental problem in nanoscale fluid analysis and furthermore, nanofluid manipulation. In this research we present the potential of digital holographic microscope (DHM) in fluid flow measurements inside nanochannels. By measuring evaporation process and fluid dewetting behavior in nanochannels as two examples, two types of experiment proecdure and data processing method is present of high resolution in height and time.