The mechanism of microfiltration of deformable submicron particles is studied. Experiments of "dead-end" cake filtration were carried out using pseudomonas suspensions. The effects of operating conditions on the filtration performance are discussed. The results show that the filtration rates increase with increasing filtration pressure, while decrease with the increase of suspension concentration. A model for cake formation is developed based on force analysis. The flux of particle deposition and the packing porosity of the formed cake can then be obtained using the proposed model. Based on the continuity equation of compression and Kozeny equation, a numerical program is established for simulating the local porosity, specific filtration resistance, and solid compressive pressure in a filter cake. The simulated values of average porosity and average specific filtration resistance of cake agree with the experimental data. It can be found that a skin layer controlling the filtration rate will form next to the membrane surface in a microfiltration of deformable submicron particles. Although the thickness of skin layer is only 10%, its filtration resistance is about 90% of the whole cake. Most compression of cake occurs at the beginning of filtration. Increasing the suspension concentration increases the particle flux of back diffusion; therefore, a thinner and more compact cake will construct under a given filtration pressure.