Abstract: In order to efficiently convert the concentrated heat of solar power tower system,three mixtures（CO₂/R290,CO₂/R600a and CO₂/R601a）are applied to the recompression power cycle.An integrated model is established for the solar power tower system,and the corresponding thermal performances are analyzed and compared under the irradiation conditions of typical days in four seasons（March20,June 21,September 23 and December 21）.The obtained results show that:in the mass fraction range of CO₂-based mixture with nonflammability,as the CO₂mass fraction increases,the system thermal efficiency,exergy efficiency and generated power of the mixtures increase first and then decrease.The optimal mass fractions are 0.7/0.3,0.8/0.2 and 0.8/0.2,respectively.Among these three mixtures,CO₂/R290（0.7/0.3）has the best performances with the thermal efficiency 18.99%and generated power 17.1 MWh at Vernal Equinox.Under different typical days,the thermal efficiency and exergy efficiency of Summer Solstice are slightly lower than those of Winter Solstice,but the generated power is the highest.Furthermore,based on the three CO₂-based mixtures,effects of turbine inlet temperature,minimum cycle temperature,hot molten salt temperature and split ratio on system performances are also investigated.It’s found that there exists an optimal split ratio to achieve the highest thermal efficiency and generated power.For the recompression power system,the optimal split ratio is in the range of 0.70-0.75.