Basing on the comparison of several methods, this paper proposed systematic steps in extraction the features of rock surface image including image enhancement， binarization, edge extracting, Hough trasformation,etc. Besides, it proposed 3 restrictive conditions to reject the redundant line segments and gave the corresponding processing flow. In addition, it developed the software to test the feasibility of the method simultaneously. The result showed that the repetition rate of the line segments reduced significantly, which could indicate the distribution of the joints more precisely.