Abstract: Fractal geometry is a new subject of graphics. By means of fractal geometry, ir-regular graphics can be studied, the self-similarity characteristics of graphs can be revealed, and quantitative data of graph self-similarity can be given. In this paper, the fractal geometry is used to analyze the flame morphology in the supersonic airflow, and the variation law of the flame fractal dimension under the condition of different equivalent ratios and fuel component molar ratios is quantitatively analyzed. The relationship between the velocity of the turbulent flame propagation and the fractal dimension of the flame boundary is studied. In this paper, the flame CH* self-luminescent transient image obtained by the high-speed photography is used to record the flame morphology of different fuels in the Mach number 2.5 supersonic airflow. The experimental results show that the fractal dimension of the frontal boundary of the supersonic combustion turbulent flame increases approximately linearly with the increase of the equivalent ratio, and increases with the increase of the hydrogen component in the fuel.