Abstract: Abstract：[Objectives]The comfort of the interior environment of the ship cabin directly affects the physical and mental health of the passengers, and also affects the working efficiency of the crew and the comfort degree of living.To improve the thermal comfort of air conditioning system.[Methods]Airpak is used to simulate and analyze the temperature, relative humidity, PMV(Predicted Mean Vote)-PPD(Predicted Percentage Dissatisfied) and air age in the four air return modes of the typical single-occupant cabin of a ship, which are different side up and down cycles, same side up and down cycles, different side down and down cycles.[Results] The simulation results show that the room temperature can be kept constant at 24℃, the humidity is kept at about 50% and the humidity field distribution is more uniform, the PMV distribution is more uniform and its value tends to 0, and the air age PPD distribution is more uniform and the value is very small in the cabin.[Conclusions] Using the optimization principle of lattice-order theory, the air return mode of the different side up and down is the optimal scheme in the single living cabin of the ship.