Diesel Particulate Filters (DPFs) provide probably the most effective means of trapping the exhaust emitted particulates from diesel engines. Three-dimension network ceramic filters become a promising alternative to the conventional wall flow filters, since they are effective in filtering small sized particles and provide a large specific surface area for catalytic coating. A mathematical model of pressure drop for a three-dimension network ceramic DPFs is developed. The model calculates the pressure drop of a filter as a function of the geometric filtering properties, operating conditions and structure of trapping. The calculated pressure drops of a filter agree well with the experimental results. The pressure drop of DPFs increases linearly with increasing trap length, and there is a nonlinear relationship between the exhaust gas mass flow rate and pressure drop. For optimized traps, the pressure drops are much lower than those of the filters with a unitary trap structure.