In recent years, the need to upgrade and increase the load bearing capacity of concrete structures has become popular due to the deterioration of constructions after long use; or due to the demand of owners. One among popular reinforcement methods today is to use Carbon Fiber Reinforced Polymer (CFRP) to strengthen the tensile zone of the concrete structure. The installation of this method is rapid and convenient. However, the technical instructions for installation is still limited in Vietnam due to the time-consuming and high cost of experiments. This research presents a numerical simulation study on the load bearing capacity of reinforced concrete beams strengthened with CFRP via the finite element method (using ANSYS APDL software) and compares the findings with experimental result afterwardss. The results show that ANSYS APDL software can accurately analyze the mechanical behavior of RC beams strengthened with CFRP. The research results can be expand to further analyze stress, deformation, and simultaneously investigate other factors that may influence RC beams strengthened with CFRP.