A mixed working medium containing monofluoroethane and trifluoroethylene belongs to the field of power engineering and engineering thermophysics. It consists of trifluoroethylene as a first component, monofluoroethane as a second component, and must be mixed with one or both other compounds. When forming a ternary mixture, any one of pentafluoroethane, difluoromethane, trifluoroiodomethane, and hexafluoropropylene needs to be added; when forming a quaternary mixture, it is necessary to add pentafluoroethane, difluoromethane, trifluoro Two of methyl iodide, hexafluoropropylene, propane, and dimethyl ether, but not any two of propane, dimethyl ether, and difluoromethane at the same time. Compared with R-404A, the multi-component mixed working medium proposed by the present invention has significantly reduced greenhouse effect potential. Its condensing pressure is equivalent to that of R-404A, and it has the technical advantage of continuing to use the main related systems or components of current R-404A. Compared with R‑404A, it has stronger thermal conductivity and smaller flow resistance, which is conducive to further optimization and improvement of heat exchangers. Its refrigeration cycle performance coefficient is higher than that of R-404A, which has energy-saving significance.