Abstract: We know that the cantilever beams are commonly used in engineering structure.Strength and stiffness should be considered in design of the structure.In the paper,the Rayleigh-Rits method is presented.It does not need direct integration which is often used in context of strength of materials.It may solve the problems of maximum stress and maximum deformation of cantilever beams with variable cross section under arbitrary loads.Two examples are presented using computer aided calculation and sophisticated equations maybe rapidly solved in the way.