Abstract: In order to improve the indoor air quality of city transport system,the authors had selected a public transport interchange station in a comprehensive transit hub as a research object. Carbon monoxide was selected as the main pollutant for description of air quality. Ventilation systems,bus traffic and passenger flow,air quality had been investigated by on-site survey. Large eddy simulation technology had been used to analyze indoor air quality of public transport interchange station. The boundary conditions were determined according to the measured date. Indoor air quality results at heights of 0. 8 m and 1. 6 m under different time periods and operating conditions of public transport interchange station were calculated. Time periods include the peak hour and trough hour.Resultshave shown that carbon monoxide concentration in peak hour is about twice than that in trough hour in most area except the rear area of the vehicle. Air quality would reach the harmful degree within 5 to 10 minutes if the ventilation system is not operating. The ventilation system should be operated during the peak hour and intermittent operation mode can be adopted during trough hour in order to meet the requirement of air quality standards.