Abstract: In order to study the diagonal shear behavior of masonry structures strengthened with engineered cementitious composites (ECC), diagonal loading tests were carried out on one unreinforced masonry wall and six masonry walls strengthened with ECC layer. The effects of strengthened forms (strengthened with single-sided or double-sided ECC layer) and the thickness of ECC layer on the shear bearing capacity of the masonry wall were analyzed. The finite element analysis models of strengthened masonry walls were established and analyzed. Then the simulation results were compared with the experimental results. Parametric analysis was also carried out using the models. The results show that the ECC layer can significantly improve the shear capacity and deformability of masonry walls. The ECC layer thickness, mortar strength and ECC tensile strength parameters have significant effects on the bearing capacity of the wall, which can provide a theoretical basis for the selection of actual engineering design parameters. The elongation demand of ECC materials that meet the deformation limit requirements of walls in the existing codes is proposed in order to provide preliminary theoretical support for the performance-based seismic design of ECC reinforced masonry structures.