Today, strengthening is one of the interesting issues in the field of building industry and its importance is increasing more and more. Beams are member of structure that are designed for flexture and shearing. They might require strengthening for various reasons such as wrong design, improper performance, excessive loading and change of structure's occupancy. There are different methods for strengthening the structure's occupancy. There are different methods for strengthening the beams such as usage of concrete jacket, addition of steel plates and usage of FRP materials. Nowadays, usage of polymers reinforced by fibres (FRP) is one of the Modern methods. In this book, different methods of strengthening the beams are explained and finally strengthening by FRP is investigated as a proper Method. This books includes four chapters, the first chapter includes introduction, the second chapter deals with the methods of strengthening the beams, the third chapter considers FRP composites and fourth chapter includes conclusion.