The filtration of soot in the metal foam DPF has been studied. INCOFOAM®HighTemp is selected for DPF material for its large specific area for filtration. The structural properties of the foam such as pore diameter, strut diameter and porosity are determined from the pictures by 3D Xray scope and SEM. The permeability and Forchheimer coefficient obtained by clean filter experiments are correlated with the structural properties. During the filtration process, the soot particles deposited inside the filter affect the local strut diameter, porosity and permeability, which determine the filtration efficiency and pressure drop. By the analytic model developed, the actual pressure drop in the engine operation can be predicted.