Abstract: The joint core area is always casted with higher strength concrete of column. The sandwich beam-column joints core area casted with weaker strength concrete of beam can simplify the construction process, but the seismic performance of the joint is impaired. To study the feasibility of the sandwich joint improved with built-in angle iron, one unimproved and one improved 3D sandwich joints were tested under bi-directional reversed cyclic loads with constant amplitude to investigate the seismic behavior, including the failure mode, ductility, energy dissipation, stiffness, strain and shear strength. The test results show that, two specimens exhibit joint failure after the beam longitudinal reinforcement yields in the joint under bi-directional loads. However, the enhancement measure increases ductility and shear strength, improves energy dissipation, stiffness declination and deformation capacity, which indicates that the seismic performance of sandwich joint is improved. Finally, the formula is presented for calculating shear strength of the sandwich joints, and the solutions agree well with the experimental results of unimproved and improved sandwich joints.