Abstract: The theory related to fractal geometry is introduced,and the simple calculation formula of fractal dimension of expansive soil particles is deduced with the presentation of their mass fractal characteristic function.Furthermore,several representative expansive soil samples of Hefei region are analyzed and handled with sieve method and densimeter method.At last the rough slope of fractal dimension value of radii of expansive soil particles is obtained,which could be the basis of further study on the character and structure of the expansive soil in this region.