This study focuses on establishing analytical and finite element models to determine the load–deflection behaviors that resulted by the combined strengthening effective of the combined of Fiber-Reinforced Cementitious Matrix composite and Fiber-Reinforced Cementitious Matrix composite. In the model, a Fiber-Reinforced Cementitious Matrix is bonded to the soffit of the RC beam and Fiber-Reinforced Polymer layers are bonded to the soffit of the FRCM layer. Theoretical formulas are attained and enhanced to identify the load–deflection behaviors. Besides, finite element models are created using ABAQUS C3D8 and T2D2 element types. The concrete damaged plasticity model is used to predict the behavior of concrete under strain loading. The deflection path curves at soffit of the beam determined through both the theoretical model and FEM are reasonable agreement, with error margin of 3.79–9.01% in comparation with those in FEM models. The scope of application of the theoretical formulation and FEM has been proposed. Implications for research on the development of the theoretical formulation have been suggested.