According to the displacement changes of measuring points with time in a underground powerhouse,the fractal characteristic of deformation of surrounding rock was analyzed,and the changing rule and trend of fractal dimension of deformation were discussed.It was discovered that maximum of fractal dimension of displacement at various measuring points all appears on the 0 + 115.60 section traversed by crack.The reason is that there are more factors causing deformation of surrounding rock on the section than on other sections,which lead to the increase of irregular degree and the existence of more complicate structures in displacement-time curve,so measured fractal dimension is larger.The result disclosed that the occurrence of maximum dimension of displacement-time curve probably is the hint and foreboding of the surrounding rock fracturing,in which measuring instrument is embedded,this can used as the criterion to judge whether surrounding rock cracks.