This talk presents a method that combines the genetic algorithm (GA) with computational fluid dynamics (CFD) technique, which can efficiently optimize the flow inlet conditions with various objective functions. A coupled simulation platform based on GenOpt (GA program) and Fluent (CFD program) was developed. Two new design methods were provided: the constraint method and the optimization method. A simple 2-D office and an aircraft cabin were evaluated, as demonstrations, which reveal both methods have superior performance in system design. The optimization method provides more accurate results while the constraint method needs less computation efforts.