The relationship of the structure and superconductivity in the system Bi,PbCa3Sr3Cu4Oy and Bi4Ca3sr3Cu4Oy is investigated. It is found that both systems belong to the material with 4334 phase identically but they have different superconductivity. The reason causing this difference may be the subtle variation coming from the arragement of atoms, the number and dis-tribution of oxygen deficiency and the feature of electrons within the cell.