Pressure drop characteristics of three fabric filters with different surface treatment, i.e. laminated with PTFE, intermingled with fine PTFE fiber, singed, were experimentally researched. It was found that the surface treatment evidently affects the dust load on the filter surface and the pressure drop across the filters. A new concept of inflection point was introduced, which is defined as the point for the pressure drop increase from nonlinear to linear. The period before inflection point is related to the penetration of particles into the filter and is much shorter with membrane filter than that of singed filter. The shorter the period before inflection point is, the less the pressure drop increases before the inflection point. Moreover, we proposed a model to express the pressure drop development after the inflection point and the results were compared with the experimental ones.