Abstract: Digital Holography Particle Image Velocimetry is a verypromising measurement technique for unsteady three-dimensional complex flow.This paper reviews the background and the research advances of thistechnology in the past two decades. Some key problems and applicationrelated problems (such as the reconstruction of the particle field, theresolution of reconstruction, the accuracy of the particle position and thedisplacement, the signal-noise ratio of the digital hologram, the opticalmethod and fast mathematical algorithms for reconstruction, and theextension of measurement volume, etc.) are discussed. At the same time,we also discuss the potentiality of off-axis digital holography and point out the development direction infuture. It is predicted that, with the rapid development of digitalcamera technique, DHPIV will become a new generation of the observationand measurement technology for unsteady three dimensional complex flows inthe coming future, and will be used for difficult problems offluid mechanics.