The mechanism of cross-now filtration of power law slurry is studied through a hydrodynamic approach. The trajectories of particles in the filtration are analyzed in order to estimate the mass flux of particle deposition on the filter septum. An agreed tendency is found between the calculated results of particle flux and the experimental data. A dynamic simulation method based upon the continuity equation of cake compression and the differential-form filtration equation of power law slurry is proposed. By substituting a set of experimental data of filtration rate vs. time into the iteration procedures, the local cake properties and their variations during a course of cross-flow filtration can be simulated. The calculated results of average cake porosity and average specific filtration resistance agree very well with the experimental data.