Abstract: Passenger density is an important factor affecting the thermal comfort environment of metro train passenger compartments. The traditional way for controlling the temperature of passenger compartments is mainly based on the UIC-553 standard, where the indoor and outdoor temperature difference is the core factor of the control. The present study constructed an integrated model which couple the passenger compartment, passengers and the air supply of air conditioners for a full-size metro train, and studied the thermal comfort of the passenger compartment by combining approaches of real vehicle tests and numerical simulations. The influence of the passenger density on the thermal comfort environment of the passenger compartment was discussed. A relationship between the average temperature of the passenger compartment and the air supply temperature of air conditioners under different passenger densities was established and the air supply temperature which can meet the human thermal comfort experience was obtained. Finally, an air supply temperature control model for the metro train air conditioner based on passenger density was proposed.