CFRP is a new kind of building materials popularly used in structure strengthening. When CFRP is used to strengthen the masonry structures built by the traditional building materials-bricks and mortar, good reinforcing effect will be achieved. But there are still a lot of theoretical difficulties in CFRP’s application in structure strengthening. The paper studied the mechanical performance of CFRP strengthening the masonry structures by finite element analysis. Ansys is used in the paper to establish discrete models of brick walls strengthened by CFRP. In the models, mortar and blocks are given different material properties and simulated by contact elements and plane elements respectively. Through the comparison of the results of finite element calculation and experimental study, the mechanical performance of the walls is studied. The study shows that contact elements can simulate the mortar very well and the mechanical performance of the discrete models presented in the paper meets the actual masonry structure well too; in addition, the strengthening material-CFRP can improve the mechanical performance of the walls effectively.