Zhongnanshan extra-long road tunnel in Qingling is large-scale and has a complex ventilation system. In order to guarantee the ventilation scheme properly and save the ventilation expenditure, the evaluation of non-mechanical ventilation effect is of importance. The research team monitored the natural wind initially, traffic flux and the wind induced by natural ventilation pressure and traffic wind force subsequently, and obtained lots of data. Through analysis of the monitoring data, we draw some conclusions: firstly, bigger speed of the natural wind occurs in the period from 10∶00 am to 14∶00 pm, and the greatest value reaches 2.576 m / s; secondly, the period of peak traffic flux in tunnel(east or west line) is mostly constant; at last, the period of bigger wind speed, which induced by natural ventilation pressure and traffic wind force, basically matches the period of peak traffic flux in the east line, while the two periods match badly in west line, meantime, the change of wind speed is relatively smooth in west line. The calculating value of the natural wind speed by method which takes account of some parameters such as wind orientation, frequency of wind orientation, the temperature of portal et al, approximates the monitoring value. The calculating value of the wind speed induced by natural ventilation pressure and traffic wind force is a little smaller than the monitoring, but approximate it.