Rutting is one of the major damage modes in asphalt pavement. Many management departments need to conduct a reasonable assessment of rutting and damage cause analysis to roads. We often use on-site observed means for assessment of road surface rutting. We use methods of on-site core and cutting specimens for laboratory analysis. This paper tell this method of determining the reasons for rutting damage by analyzing the porosity, sub-layer uplift factor, size distribution, whetstone ratio and rutting test results.