Roughness is an essential factor in the rock joint mechanical behavior, which can be acquired in destructive back-analysis tests or non-destructive profile analysis. The conventional non-destructive way to estimate joint roughness in field survey is by capturing the geometry with profilometers and then comparing it with Barton’s standard profiles to obtain the JRC value. However, it is subjectively and qualitatively. Profile analysis is an alternative way to calculate quantitative joint roughness. The well-known one is proposed by Tse and Cruden, who evaluate roughness based on the local slope of the profile. It is complex and challenging to utilize in the field survey because it requires fine profile sampling. Therefore, we investigate the performance of a simple a/L method on roughness estimating. The a/L method can be implemented in the field survey because it requires only the amplitude and length of a joint profile. In this study, we first collect joint profiles from sites and then calculate the joint roughness by using the a/L method and the Tse-Cruden method, respectively. The results are compared with the manual rating roughness, which shows that the a/L and Tse-Cruden methods are deviated. In addition, two different corrections of a/L method are proposed to modify the results, which is close to manual rating after modification.