The energy separation characteristics of vortex tube installed with flow straightener were experimentally investigated for better promotion of the application of vortex tube in the improvement of energy efficiency and sustainability. Systematic evaluation of the vortex tube with straightener was performed by applying a combined method of energy as well as exergy analysis, and the temperature separation process facilitated by the flow straightener was analyzed in depth. The effects of cold mass fraction (μc = 0.2–0.8), blades number (N = 0, 2, 4, 6 and 8), diameter ratio (ε = 0, 0.2, 0.4, 0.6 and 0.8), blade angle (θ = 0°, 30°, 60° and 90°) and installation position (Ls/L = 0.25, 0.45, 0.65 and 0.85) on cold and hot temperature differences, coefficient of performance, exergy efficiency and internal temperature field were investigated experimentally. The results show that as the blades number, blade angle and installation position increase, the cold and hot temperature difference and coefficient of performance first ascend and then descend. The presence of a hole in the center of flow straightener weakens the energy separation performance of vortex tube. A flow straightener with 4 blades, 0 diameter ratio, 60° blade angle and 0.65 installation position produces optimum energy separation performance and exergy efficiency.