To address the low energy efficiency and significant performance reduction under high-temperature conditions of ejector refrigeration cycles (ERCs), this study proposed a novel booster-assisted ejector refrigeration cycle integrated with a vapor-liquid separator that exhibited a higher unit refrigeration capacity and reduced generator heat input. A thermodynamic analysis was conducted to compare the proposed cycle with two existing booster-assisted ejector refrigeration cycles, and the applicability of four environmentally friendly refrigerants was systematically evaluated. The results demonstrated that the improved cycle enhanced the performance by reducing the evaporator inlet vapor quality through vapor-liquid separation. Under typical operating conditions (generation temperature: 80 ℃, condensation temperature: 35 ℃, and evaporation temperature: 0 ℃), the proposed cycle achieved a coefficient of performance (COP) of 1.198, showing significant improvement over conventional cycles. R1234ze (Z) was identified as the optimal refrigerant because of its low Global Warming Potential (GWP) value and superior thermodynamic properties. A parameter sensitivity analysis revealed that the COP of the improved cycle increased with rising condensation temperature (from 1.168 at 30 ℃ to 1.232 at 40 ℃), whereas conventional cycles exhibited an opposite trend. When the generation temperature increased from 70 ℃ to 90 ℃, the COP of the improved cycle decreased by 28.6%; however, its refrigeration capacity remained higher than that of conventional cycles. This study provided a theoretical foundation for enhancing the energy efficiency of low-grade heat-driven refrigeration technologies and promoting the application of eco-friendly refrigerants.