The effects of particle size on the cake properties and the performance of cross-flow microfiltration are studied. A particulate sample with a wide size distribution range from submicron to micron is used in experiments. The probabilities of particle deposition are analyzed based on a force analysis. Since the major forces in determining the particle deposition and packing in the filter cake are different for submicron and micron particles, the particle size plays an important role in the filtration performance. Cake properties, such as mass, porosity and average specific filtration resistance of the cake, are calculated theoretically and compared with experimental data. Except for the overestimation of the mean particle size for about 1 mu m, the calculated results of the pseudo-steady filtration rate and cake properties under various operating conditions agree fairly well with the experimental data.