A Method for collecting SO2 and CO2 in flue gas from coal-fired power plant and producing chemical products, comprises the process of desulfurization and decarbonization by taking ammonia as an absorbent and the process of producing soda ash and other chemical products by taking sodium chloride as a crystals forming agent, in particular includes a step of desulfurization process, a step of decarbonization process,a step of exhaust treatment; a step of sulfur by-product recovery, a step of carbon by-product recovery and a step of CO2 desorption. The invention realizes the removal of SO2 and emission reduction of CO2 from coal-fired power plant, effectively solves emission problems of environmental pollutants in coal-fired power plant, changes the traditional model of producing low value by-product, provides a recycling method to extend the power generation industry chain and the process routes of producing bulk chemicals from desulfurization and decarbonization by-product, having a good application prospect.