Effects of dry grinding, wet grinding and wet grinding after fermentation on the physicochemical properties of mung bean were studied. The results indicated that the composition of wet ground mung bean after fermented flour (FWMB) changed the most, protein content decreased from 23.68% to 21.02%, the starch content decreased from 56.97% to 55.11%, and the amylose content increased from 14.48% to 19.72%. The analysis of pasting and hydration properties showed that wet ground mung bean flour (WMB) and FWMB had higher peak viscosity, minimum viscosity, attenuation value and final viscosity than dry ground mung bean flour (DMB), and water absorption index and swelling power were increased, but water solubility index was decreased. Particle size analysis found the average particle sizes of DMB, WMB and FWMB were 120.13, 105.21, 92.94 μm, respectively; scanning electron microscope observation showed that the ultrastructure of WMB and FWMB was relatively intact, while DMB had the greatest damage; damaged starch content confirmed WMB, FWMB and DMB were 9.92%, 5.99% and 6.07%, respectively. It indicated that wet grinding and wet grinding after fermentation can improve the pasting viscosity and hydration properties by reducing the damaged starch content and average particle size of mung bean.