Because of lateral sparse wave, there is structure difference between central region and periphery in explosive welding interface. However, academic estimations for the difference of interfaces morphology are still in the qualitative level, quantitative analysis methods have not been established. This paper tries to evaluate the difference of explosive welding interface morphology quantitatively. First of all, an elastic-viscous model was established to analyze the forming of wavy interface, and symmetrical 2024 Al explosive welding was carried out for testing. Then the interface images of both central district and periphery were detected by three-dimensional ultra-depth microscopy, and a demarcation line for the central area and periphery was defined based on the impact impulse. Furthermore, the fractal dimensions and multi-fractal spectrums of the images were calculated on the basis of fractal theory. According to the physics meaning of fractal characters of images, the quantitative descriptions have been achieved for explosive welding interface structure difference.