The influence of longitudinal wind on natural ventilation with vertical shaft in a road tunnel fire was investigated numerically by Large Eddy Simulation. The smoke flow characteristics of a road tunnel fire under the combined function of longitudinal wind and stack effect of shaft were analyzed. Results show that the stack effect, plug-holing and boundary layer separation are the dominating factors on the natural ventilation performance. Plug-holing occurs at small longitudinal velocity and causes the reduction of exhaust effect. At high longitudinal velocity, the driving force of smoke exhausting is weak and obvious boundary layer separation occurs, resulting in a poor exhaust capacity. There is a critical value of longitudinal wind velocity, in which a better smoke exhausting effect can be obtained. (C) 2012 Elsevier Ltd. All rights reserved.