Abstract: To investigate the efficiency of solar chimney for natural ventilation and fire smoke extraction in urban tunnels,numerical simulation was used to study the effect of chimney height,cavity clearance,solar radiation intensity and fire power on the ventilation and smoke extraction efficiency. The study results show that the natural ventilation rate of the tunnel increases with the increase of chimney height,cavity clearance and solar radiation intensity,and the ventilation rate increases by 17% for every 1.4 m increase in chimney height,16% for every 0.5 m increase in cavity clearance,and 11% for every 200 W/m~2increase in solar radiation intensity.The efficiency of the solar chimney for smoke exhaust is better than that of the traditional shaft,and the effect of chimney height on the efficiency of smoke exhaust is smaller,and the critical value of the cavity clearance for smoke exhaust is 1.5 m. Based on the transverse asymmetric parabolic temperature distribution inside the solar chimney,a prediction model for the volume flow rate at the exit of the chimney is proposed.