In order to realize high-precision digital holographic phase unwrapping, a lightweight deep learning network based on MobilenetV3 integrated in the Unet network framework adopted, and the UMnet network designed to realize accurate unwrapping of holographic phase. The network lightweight attention mechanism and multi-scale convolution to enhance the network accuracy and generalization ability. At the same time, the hard-Swish activation function improve the network learning ability. The simulated data set used for network training, and the noise reduction ability of the generated network model tested, which verified by the test of the hologram of the actual sample. The results show that the structural similarity index of UMnet is 6.6% higher than that of deep learning phase unwrapping network. UMnet can realize digital holographic phase unwrapping simply, quickly and efficiently.