Abstract: Different from SO₂ and NO_x ultra-low emission technologies, PM ultra-low emission is the result of the interaction of multiple treatment processes which is a system engineering, so it is necessary to consider the applicability and effectiveness of the primary dust removal and secondary dust removal technology together. At present, PM ultra-low emissions technical route of the coal-fired power plants has been diversified with the development and application of new technology of dust removal and new technology of desulfurization which has synergistic effects for the dust removal. In the past, wet electrostatic precipitator(WESP) dust removal technology as secondary dust removal was the main technology to achieve the ultra-low PM emission, but now the wet desulfurization technology having synergistic effect for the dust removal as secondary dust removal and the electric bag composite dust removal technology able to achieve the ultra-low PM emission by primary dust removal have been applied in the coal fired power plants. The development and application status, effect and applicability of primary and secondary dust removal technology were analyzed, and the principles and methods to choose the ultra-low PM emission technology for coal-fired power plant put forward.