The influence of the interaction between two structural blocks on superconductivity was studied by calculating the cohesive energy in Bi-system superconductors, Bi2Sr2CuOy (2201), Bi2Sr2CaCu2Oy (2212), and the Bi2Sr2Ca2Cu3Oy (2223) phases, and Hg-system superconductors, HgBa2CuOy (1201), HgBa2CaCu2Oy (1212), HgBa2Ca2Cu3Oy (1223), HgBa2Ca3Cu4Oy (1234), and HgBa2Ca4Cu5Oy (1245), respectively. We developed a program to calculate the combinative energy between Cu-O planes and remaining parts, and between blocks in the superconductors. The result indicates that if we consider the cell as two blocks combined together, a close relationship among the combinative energy between the two blocks, the value of Tc, and the number of the Cu-O planes in the Bi-and Hg-system superconductors is established. The result gives an interesting way to understand the change of the value of Tc as the number of the Cu-O planes. In contrast, the combinative energy between the Cu-O planes and the remains obtained from the method separating all the Cu-O planes from the cell and leaving some discrete remaining parts does not show any relationship with the value of Tc. This means that considering the cell as the two blocks is more reasonable, and the interaction between the two blocks plays an important role in superconductivity.