This paper relates to the semi-empirical model based on fire field energy balance and the physical model based on land temperature,aiming to provide a practical way of describing fire spread.Fire spread is determined by the characteristics of combustible materials and the agency of meteorological factors and terrains.Combustible materials,such as surface area,have no featured scale,yet the process of forest fire spread contains the self-replicating feature,both of which contribute to the self-similarity of fire spread.Consequently,fire behavior can be described by fractal geometry.In this research,we select Wuchagou forest in Da Hinggan Mountains as the experimental site where a forest fire took place three years ago.The forest fire was detected on low-resolution NOAA-AVHRR images,and fire spread was simulated on high-resolution TM images as another attempt to merge information.Based on remote sensing and GIS,we adopted the method of limited spreading lumping (DLA) to describe growing phenomenon to simulate the dynamic process of fire spread and adjusting shape of the result of fire simulation by the scale rule.As a result,the simulated fire and the actual fire manifest the self-similarity in their spreading shapes as well as the quantitative similarity in their areas.