Abstract: At present, the study of rock structural surface roughness is often confined to the earth's surface. So, it is difficult to reflect the characteristics of the deep rock joints roughness. The drill wall joint profile contains the characteristics of 3D information. This paper has carried out the research of fractal characteristics of rock joints roughness based on the digital borehole camera technology, obtained panorama of underground drilling rock joints using digital camera system, extracted rock joint contour line using edge detection technology, then got the real rough surface contour by space transformation and distance transformation. This paper has got the JRC value of rock joint contour line by compared with the 10 contour line profile curve which Barton had put forward and calculate their fractal dimensions. According to the principle of least squares method, we can fit the relationship between the fractal dimension and JRC and that is (D)=JRC=-541.9x2+1362x-818.53. This paper has provided the basis for describing the structure and characteristics of the deep-seated natural joint. The results is important significance because it is meaningful for the more in-depth study about the surface of the rock joint which is located in deep underground.