In order to choose the most economical and efficient airliner environmental control system, several types of air cooling systems for the modern airliners were optimized and compared. The optimized mathematical models of two wheels system with low pressure water separation, three wheels system with high pressure water separation and four wheels system with high pressure water separation were established respectively. The fuel oil loss for airliner environmental control system is taken as the objective function. Generalized multiplier combined with simplex method is used to seek the optimum solution. The optimized results can be used as the theoretic foundation for the design and research of airliner environment control system.