Abstract: Rock fall is a common-place topographical phenomenon and makes a large socio-economical impact.Rock-fall hazard is difficult to assess because it is impossible to predict the exact trajectory of any one block of rock.This paper analyzes and compares some model about rock-fall which have already exsited.Based on a model named cone，we have developed the program to estimate the area of rock-fall，and have taken some precautionary measures according to it.