Considering the lack of investigation on the dynamic distribution characteristics and the law of formaldehyde under the ventilation condition in passenger cars， this paper applied Computational Fluid Dynamics（CFD） theory and Fluent software to establish a numerical simulation model for analyzing formaldehyde concentration and its distribution in vehicles， and verified its reliability. On this basis， the present work firstly studied the distribution and dynamic variation of formaldehyde mass concentration in passenger vehicles based on the analysis of the air flow field by taking temperature， ventilation rate and ventilation mode factors as variables. Especially， this study investigated the influence of temperature， ventilation rate and ventilation mode on formaldehyde mass concentration at the breathing positions of drivers and passengers， as well as some typical sampling lines in vehicles. The results indicated that the temperature has a significant effect on the formaldehyde concentration in a car. It was also found that formaldehyde concentration at 0.5 m/s and 4.0 m/s ventilation rates presented different distribution characteristics of “hyperbola” and “hump”， respectively， due to vortex flow field. Formaldehyde mass concentration at the driver’s breathing position increased with the increase of ventilation rate. When the ventilation rate is not larger than1.6 m/s， the growth rate is 16.5%； When the ventilation rate is larger than 1.6 m/s， the growth rate decreases to 3.6%. The formaldehyde concentration at the vehicle detection point showed a linear growth trend with the air velocity rate at growth rate of 10.8%. The formaldehyde concentration in the rear row is higher than that in the front row in a car.