Abstract: Analyze the investigation process of a Wildland-Urban Interface fire in China. The investigators first determined the basic situation of the fire through investigation, inquiry, and preliminary investigation. They used drones to take high-altitude photos and drew a U-shaped trace map of the fire spread, and divided the key area based on the terrain of the fire site. Subsequently, the investigators used grid search technique, loop search technique and other methods to conduct sectional inspection of the divided area, and finally found key fire evidence in the key fire source area. The analysis confirms that the fire was caused by an artificial picnic bonfire that was not properly extinguished and ignited surrounding combustibles. Through the analysis of the investigation process of the fire, the shortcomings and inspirations in the investigation process were summarized, in order to provide reference for the investigation of such fire accidents.

Key words: Wildland-Urban Interface, fire investigation, fire cause