Abstract: Using the CFD-WindNinja model in conjunction with topographical data, a small-scale wind field numerical simulation was conducted for a forest fire that occurred near the Lushan Mountains in Xichang City, Liangshan Prefecture, on March 30, 2020, and the influence of terrain on the wind field was explored. The results indicate that: (1) The small-scale model demonstrates high precision in simulating wind fields, clearly illustrating the specific effects of terrain on mountain wind fields. (2) On the windward slope, the fire site experiences increased wind speeds, intensifying the upward spread of the fireline. (3) Wind fields parallel to U-shaped wide valleys generate strong mountain-crossing airflows, while wind fields perpendicular to V-shaped narrow valleys are prone to causing "spot fires" during wildfire processes. Wind parallel to V-shaped valleys accelerates within the valley. (4) Mountain winds are prevalent at night, while valley winds are dominant during the day. Additionally, when valley winds transition to mountain winds, the increase in wind speed intensifies fire spread in complex terrains.