The current status of existing flue gas purification systems of the municipal waste incineration power plants was analysed in this paper. Two feasible ultra-low emission improvement technical routes were proposed, i.e. circulating fluidized bed desulfurization and high efficiency synergistic wet desulfurization technology, based on the similarity of the flue gas properties between the coal-fired power plant and the municipal waste incineration power plant and the advantages of the ultra-low emission systems of the coal-fired plant. Further, the capital and operational costs of the two corresponding technical routes were evaluated. The results indicated that the capital investments of the two technical routes were equivalent, about 13700yuan per ton. For the operating cost, the route based on wet desulfurization was higher, about 16.46yuan per ton. If the government adopts the policy of environmental electricity price subsidy, the capital expenditures caused by the ultra-low emission improvement investment and operation of these two routes could be made up for within three years and seven years, respectively.