In this article, we verify the existence and uniqueness of solution for a class of nonlinear boundary value problem for fractional differential equation of order , with the standard fractional derivative in the sense of Riemann–Liouville. By using a variety of tools including the Schauder fixed-point theorem, the Krasnoseĺskii fixed-point theorem and contraction mapping principle, existence and uniqueness results are obtained. Some examples are given to expression the results.