The review of tunnel ventilation systems was presented and the latest related researches in the countny and abroad were introduced.Two numerical simulation methods were proposed to analyze the piston effect in the tunnel:dynamic mesh and momentum source method.The dynamic mesh method can reveal the real motion of vehicles and provide a detailed information of local parameter changes in 3-D space,however,much time should be taken for simulation and the efficiency is low.The momentum source method can achieve the vehicle motion by adding a momentum source.The latter method can avoid the large consumption of computing sources and time and can improve the simulation efficiency greatly.