In order to improve the thermal efficiency of the supercritical CO₂ recompression Brayton cycle (SCRBC), an organic flash cycle (OFC) was coupled at the waste heat end of SCRBC as the bottom cycle for low-temperature waste heat utilization, and a solar tower-based SCRBC/OFC combined cycle was established. Under the set conditions, parameter analysis and exergy analysis were conducted on the effects of the main parameters of the combined cycle such as the split ratio, top-cycle turbine inlet pressure and temperature, turbine efficiency, flash temperature, and condensation temperature on the thermal performance of the system. Parameter analysis results show that there is an optimal split ratio at different top-cycle turbine inlet pressures and temperatures, and the optimal split ratio increases with the increase of turbine inlet pressure. The thermal efficiency of the system decreases with the increase of condensation temperature, and as the flash temperature increases, the thermal efficiency first increases and then decreases. The exergy loss analysis shows that under the given condition, the printed circuit heat exchanger (PCHE) has the highest exergy loss, followed by the SCRBC turbine, precooler, and reheater. A multi-objective optimization method was used to obtain a Pareto solution set that takes both system thermal performance and unit investment cost into consideration, and the optimal compromise solution was provided as a reference for engineering design schemes. The optimized SCRBC/OFC improves the thermal efficiency of the combined cycle by 12.5% compared to the unoptimized SCRBC.