Research conclusions : The basalt along the railway often locates on the earth s surface and lies into sand, gravel and clayish soil, tertiary clay stone and sandstone. The basalt covering the mountaintop generally forms unstable steep cliff, which is the main source of avalanche and rock falling. The avalanche degree of basalt relates to undersurface stratum， that is to say, adverse hillside is easier to produce avalanche and rock falling than bedding hillside. The shape of fallen rock is usually block shape and anomaly ball and its appearing probability is opposite to the volume.