The invention relates t a method for selective oxidation removal of CO, and a method and a system for preparing acrylic acid through one-step oxidation of propane. According to the method for selective oxidation removal of CO, a composite oxide comprising at least two materials selected from CuO, CeO2, Co3O4, FeOx, NiO, MnOx, VOx, ZnO, La2O3 and MoOx is used as a catalyst, and the catalyst and mixed gas containing CO, O2 and at least a hydrocarbon are subjected to a contact reaction to remove CO. The method for preparing acrylic acid through one-step oxidation of propane comprises a propane selective oxidation reaction step, a crude acrylic acid separation step and a tail gas treatment step, wherein the tail gas treatment step comprises that the tail gas is recycled for the propane selective oxidation reaction step after the tail gas is subjected to dewatering and selective CO removing. The system for preparing acrylic acid through one-step oxidation of propane comprises a tail gas treatment assembly, which is connected to a product separation assembly and a raw material pre-mixing assembly. According to the present invention, CO with high explosion risk in the tail gas is selectively removed while propane and propylene are retained, and the high CO content tail gas produced in the process is effectively treated and recycled, such that the industrialization for preparing acrylic acid through one-step oxidation of propane can be easily achieved.