In order to simulate the fluid flow in a porous filter in a dust removal facility, gas velocity and pressure distributions in the filter element at T = 673 K and P-e = 20 atm were calculated numerically for both steady and non-steady states. The effects of the diameter and length of the filter element on those distributions were also studied. The size of a porous filter had influence on the baseline pressure loss and the distribution of flow in the filter during filtration and cleaning. Filter size was, however, restricted by cleaning performance because a large amount of cleaning gas had to be flushed into the internal filter. As the length of the filter increases and the diameter decreases, total pressure and the inlet velocity of the cleaning gas increases rapidly. It can produce an insufficient cleaning effect, forming cleaning velocity distributions within filter. In an analysis of the transient region from filtration to cleaning, the flow in the filter approached steady state in 50 ms after injecting pulse jets. initially after injecting pulse jets, the pressure was relatively high at the inlet regime of filter.