At 02:00 BT 28 February 2007, a train of No.5807 from Urumqi to Aksu encountered terrible gale winds, which were caused by northerly cold wave, at the socalled 30 km wind gap in Xinjiang, leading to that the 11 carriages were derailed and overturned. By using mesoscale model WRF, a numerical simulation was made for the gale process. The results show that the WRF can simulate the variation and distribution of the gale in the 30 km wind gap, but the wind velocity of simulation is lower than that of observation, and variation trends of wind velocity are nearly to observations. It may be concluded that the high pressure gradient and special landform are the main reasons of the gale. Meanwhile, both funnel effect and downslope wind also exist.