Based on the developping disciplinarian of karst,it is pointed out that distortion and water damage are two basic types of Subgrade damage,and asymmetric settlement and stability lose of subgrade are the material reflections of karst subgrade damage.According to the karstic characters of X1 where clint,funnel,billabong,dissolved cavern and karstic spring existe at the same time,considering the scale effects of karstic configuration,abiding by the preventting and disposing principles by dredging and leading,spanning,reinforcing and jamming,the disposal material measures for karst subgrade of X1 section are put forward.