Polyimide fiber in the field of environmental protection is the main purpose is as industrial high temperature dust filter material, polyimide fiber is a significant feature of its irregular cross-section structure. Application of special processing parameters in the spinning process can be obtained irregular cross-section of the trilobal cross-section fiber structure, the formation of a very high fiber surface area coefficient. Fiber surface area increased by about 80% compared to the circular cross-section fiber, greatly increasing the ability to capture dust particles and improve the filtration efficiency. And the special fiber cross-sectional morphology, making the dust mostly concentrated to the filter surface, the more difficult to penetrate into the filter media inside the plug the pores, reducing operating resistance. So the polyimide fiber on the dust collection capacity is much stronger than the general fiber. Coupled with excellent chemical properties of polyimide, oxidation resistance, low water absorption, heat resistance and dielectric properties, making polyimide become the best high-temperature flue gas filter material, competitive advantage.