Abstract: In order to study the ventilation characteristics of tunnels with spiral structure, taking a high drop and spiral tunnel in Yunnan as the research target, this paper conducts numerical simulation and analysis of the tunnel ventilation conditions under different working conditions. The study results show that the distribution of ventilation airflow in the tunnel, as a whole, is not significantly affected by the spiral structure of the tunnel, but the longitudinal attenuation characteristics of the airflow velocity at the inner and outer sides of the tunnel are not the same within the working area of each jet fan, and a certain level of air backflow occurs. Under fire scenarios, the smoke has a smoke back-layering zone with length of around 30 m and the average airflow velocity in the tunnel is higher compared to that under normal ventilation conditions.