Based on the requirement for real-time,online detection and analysis of dynamic digital holography,in this paper,a fast phase unwrapping algorithm used in dynamic digital holography is presented.We find out the inaccurate points affecting unwrapping accuracy while fully considering phase unwrapping accuracy and running time,make some marks for them,and then use the center radiation phase unwrapping algorithm,which has relatively fast operating speeds to bypass these inaccurate points.In order to solve the relevance problem in time domain for phase values of different frames and the phase unwrapping problem for inaccurate points enclosed area,we use the relevance in time domain of dynamic digital holograms after setting the unwrapping path in time domain.Experimental results show that this algorithm is reasonable and effective.It has a fast speed and high accuracy in phase unwrapping.