The thermal economic performance model of the system is established by using the low-temperature gas at the outlet of the end of the annular cooler as the organic Rankine cycle ( ORC) heat source，and the pure working medium R600 and R601a are selected to form the mixed working medium，and the effects of different mixed working medium mass fractions and key parameters of ORC on the thermal economic performance of the system are studied. The results show that， for a given ORC key parameter，with the increase of the R601a mass fraction ( M_R601a ) in the mixed working medium，the net output power ( W_net ) and exergy efficiency ( η_ex ) of the system first decrease and then increase，while the levelized energy cost ( LEC) of the system first increases and then decreases. When M_R601a is constant，the system Wnet first increases and then decreases with the increase of evaporation temperature ( T₆ ) ，and decreases steadily with the increase of superheat ( ΔT_7-1 ) . The higher the T₆，the lower the ΔT_7-1 and the greater the ηex of the system. The LEC of the system gradually decreases with the increase of T₆，and decreases first and then increases with the increase of ΔT_7-1 In the variation range of MR601a and ORC key parameters，the system Wnet and ηex of pure working medium R600 are the largest，showing better thermal performance，while the system LEC of pure working medium R601a is the smallest，showing better economic performance