Abstract: A new method with use of normal vector unit cycle to assess rock fracture roughness on linear profiles is proposed. A new concept of orientation roughness is put forward to reduce data dimension from 2D to 1D. The roughness quantitative description takes the form of weight mean value and weight variance of orientation. The two parameters can reflect contribution of each differential length. The bigger the orientation roughness, the rougher the linear profile. The new method with other exiting methods, are used to assess several regular and irregular linear profiles. The results show good uniformity, which indicates the new method is right and can be used to assess rock fracture roughness.