Abstract: To reveal the pulsate dust-purging mechanism of plenum-type bag filter, the adiabatic energy equation based on aerodynamics is applied to the venting system, so as to drive theoretically the reverse air speed expression of bag filter surface in pulsate dust-purging process. Then, the removing force due to reverse airflow, which is acting on the dust layer on bag filter surface, can be obtained. And the relationship between the removing force and dust removing rate is given to the data resulting from the test of bag filter model. In this way the reverse air speed and air flow rate for purging are available to obtain, which are both necessary to the preset removing rate under conditions that the dust burden of bag filter is constant. The investigation results provide a reference necessary to the design of dust-purging system.