The Y₂O₃-BaO-SrO-CuO system was found to have the superconducting phase Y(Ba_1-xSr_x)₂Cu₃Oy where x ranges up to about 1.5. Another new ternary compound Sr₃Cu₅O_δ was identified. This phase has orthorhombic structure with lattice constants a=3.950Å, b=13.376Å, and c=11.468Å, and solid solution region enclosing Sr₃Cu₅O_δ, YSr₂Cu₅O_y, and BaSr₂Cu₅O_z.