In order to consider the influences of strength parameter's randomness of rock-soil body materials on slope stability, the traditional slice method was replaced by the slope stability integral method, which could avoid calculation errors caused by the different soil slices in the slice method. The interval analysis theory was utilized with full consideration in the randomness of shear strength parameters of rock-soil body in order to obtain the equations of interval safety coefficient under a certain range of soil parameters and slope interval safety coefficient under the condition of submerging. The Matlab was used to compile the programs. The numerical example showed that, the safety factor obtained by the conventional method was included in the value range obtained by this method, which showed that the method was reasonable for the homogeneous slope, and the interval results were of practical engineering significance.