The purposes of this study are developing a stress index for each individual major trail in the national parks and contribute to establishing a park management policy based on scientific analyses using the index. We collected data from 144 sections of trails in national parks, conducted the Delphi survey and factor analysis, and generated the stress index by standardizing scores of factors contributing to the stress for each trail. As aresult, total eight factors contributing to the stress were considered and four of them, i.e. the amount of visits, the effect of visits, the degree of trail destruction, and species diversity, were selected to generate the stress index. How to weigh factors was determined by their importance obtained in the second Delphi survey and the average from a 5 point Likert scale. Then, the cumulative probabilities from the standardized scores were graded into five groups. In conclusion, there were twenty trails from the six national parks including Jirisan, Bukhansan, Deogyusan, Naejangsan, Seoraksan in the first grade which gained over 80 as the stress index.