Abstract: Since the dust cake formed from the settling of dust particles exert impact on the filtration pressure loss, the dust cake is regarded as a new collector. The filtration pressure loss under clean condition is compared with that under dusty condition, and a math model of filtration pressure drop of non-stationary is developed. The experimental data reveal that the theoretical value computed by using the math model is basically in agreement with the experimental value. Baesed on the test of pressure loss in non-stationary filtration, a semiempirical formula for computation of the pressure loss increment in non-stationary fitration when using common home made filtration media so as to estimate the change of the filtration pressure loss and duration of operation. Timely cleaning or replacing the filtration media can prolong the service life of the filtration bag.