Abstract: A quantitative relationship between critical temperature of A-15 superconductors and single-phase Ba₂RECu₃O_9-δ superconductors and their component elemental atomic charge-radius ratio was obtained by using bonding parameter topological index and linear regressive method. The improved molecular topological indes ’H_th was advanced to analyse the effect of atomic interaction between cell and secondary cell on critical temperature Tc of superconductors.