This　paper　presents　a　new　design　method　for　turboexpander-compressors　used　in　air　refrigeration.　As　a　key　component　of　the　reverse　Brayton　cycle,　the　efficiency　of　the　turboexpander-compressor　significantly　has　an　impact　on　the　overall　cycle　performance.　The　expander　section　is　optimized　for　multi-objective　efficiency　at　different　flow　rates　using　the　Imperialist　Competitive　Algorithm　to　achieve　high　performance　across　all　operating　conditions.　Regarding　achieving　high　utilization　efficiency　for　output　power　from　efficient　expanders,　the　compressor　section　adopts　combined　methods　involving　the　jet-wake　model　and　parameter　equations.　The　proposed　design　is　validated　through　public　models,　computational　fluid　dynamics　simulations　and　experiments.　Simulations　and　analysis　are　conducted　on　test　cases　representing　comprehensive　operational　scenarios　for　both　the　compressor　and　the　expander,　confirming　that　conclusions　drawn　based　on　this　method　align　well　with　underlying　theoretical　principles.　At　the　design　mass　flow,　the　expander　efficiency　is　89%,　and　the　compressor　utilizes　the　output　power　of　the　expander　with　an　efficiency　of　90%.　Near　the　design　flow,　the　expander　efficiency　is　more　than　85%,　and　the　compressor　utilizes　the　output　power　of　the　expander　with　an　efficiency　exceeding　80%.　This　paper　presents　a　method　for　turboexpander-compressors　applicable　to　air　refrigeration　cycles,　which　achieves　a　reduction　in　design　costs　and　an　improvement　in　efficiency　under　varying　loads.