Aimed at the problems that helicopter cockpit is narrow in space, passengers are high at density of population and thermal load is heavy, and multiple passengers are thirsty for introducing a fresh cooling air of thermal comfort, an optimization design of air conditioning and ventilation system for cabin is proposed. In view of the typical helicopter cockpit layout, a three\|dimensional model of cabin and crew is built. Defining the occupant ambient temperature, temperature deviation, occupant ambient speed, PMV (predicted mean vote) and air age as thermal comfort evaluation indicators, three different layout schemes of air conditioning and ventilation systems are designed and calculated, and the optimal layout scheme is selected through the comprehensive comparative analysis of thermal comfort evaluation indicators. On the basis of the optimal layout scheme, the multi\|objective genetic algorithm is used to define the double objective function based on PMV and air age, and the simulation optimization of the location parameters of the air supply outlet of the air conditioner is carried out. Through the analysis of the result data and Pareto front, the optimal location parameters of the air supply outlet of the air conditioner are determined, and the optimal design of the cabin air conditioning and ventilation system is completed. And the accuracy and effectiveness of simulation are verified.