[en] The composition dependence of superconductivity and crystal structure in La(Ba_1-chiCa_chi)₂Cu₃O_7-y system was determined by the resistivity measurements and X-ray diffraction analysis. The superconducting transition temperature is raised with the increase of Ca content till chi=0.6, at which the zero resistance temperature of the sample is 81.5Κ. In the meanwhile, the crystal structure of the sample changed from tetragonal (chi=0) to orthorhombic structure (chi=0.2,0.4,0.6). With further increase of Ca content, the superconductivity decrease for the sample of chi=0.8 with mixed phases including the orthorhombic oxygen-deficient perovskite-like (ODP) structure and no superconducting transition is found at 4.2Κ for the sample of chi=1 without the ODP structure. A possible explanation of these experimental results is given