The main theme of this thesis is oriented toward three objectives. The first objectives, is to study and illustrate the basic properties of fractional calculus such as differentiation and integration. The second objective is a study of fractional differential equations of the form: y(a) = f(x, y), y(a-k)(x0) = y0, k = 1, 2,...n+l, n < a < n + 1 as well as their basic properties and methods of solution with some modifications. The third and main objective of this thesis is to study the varitional approach for solving fractional differential equations and how to formulate such type of differential equations in operator form as well as the variational formulations. This have been done with the novelty of evaluating the varitional formulation related to the fractional differential equations without transforming the fractional differentials equation to a fractional integral equations of volterra type.