Application of carbon fiber material to reinforced concrete structure is a systems engineering involving materials, design and application, which is also an applied science involving numerous subjects. Carbon cloth is used to reinforce structures in many projects, but the study on strengthening frame joints is still little. Especially the study on aseismatic performance of frame structure side joints is much less. In this paper, the author established constitutive relation of RC frame side joints strengthened with carbon cloth and made a numerical simulation analysis of four side joints of beam column plate under low-cycle repeated load with ANSYS, a software based on finite element analysis. The author analyzed the failure mode and the mechanism under stress, found out the characteristics of hysteretic curve of such kind of joints, acquired ductility coefficient and equivalent viscous damping ratio coefficient and studied the structure ductility and seismic-energy-dissipating capacity. It was shown that failure mode transited from shear brittle failure of core space to ductile failure of plastic hinge of beam end, joints’ seismic-energy-dissipating capacity and ductility were improved observably, joints’ displacement between layers was reduced, and rigidity and aseismatic capacity of component were improved after the joints’ being reinforced with carbon cloth. And aseismatic performance of structure was superior obviously.