Abstract: This paper analyzed and summarized karst formation mechanism and growth regularity on the basis of detailed investigation and indoor study of geological disasters of he Dali-Ruili railway in Machang and Daojieba Sheet. The complex geological structures, soluble carbonate, hot and humid weather and abundant precipitation all provide favorable conditions for the development of karst landform. There are surface karst funnel and large underground karst caves in the study area, and they will bring great harmfulness to railway and railway tunnel. Since many sections have karst development conditions, it is necessary to carry out detailed karst investigation along railways.