In the last few decades increasingly more diffusion process were found not to obey the classical Fickian diffusion equations.Recent studies show that the fractional diffusion equations provide an adequate and accurate description of these anomalous diffusion processes,which cannot be modeled properly by second-order diffusion equations.Recently,there has been increasing interest in the study of fractional calculus for its wide application in many fields if science and engineering,such as the physical and chemical processes,materials,biology and so on.