Abstract: The free electron approximation model can be used to calculate the electronic density of state of low temperature superconductivities Nb3Sn and Nb3Al but the mole fraction or atom-volume ratio fraction methods are effective methods for high temperature MgB2 and YBa2Cu3O7 superconductivities. The smallest value of the Debye temperature of many compounds depends only on the atom-volume ratios. However, the initial Debey temperature can evaluated from the smallest value and a constant related to the interaction coupling between electron-phonon for the components of compound, this result is a reasonable and approximately value close to experimental value of initial Debye temperature.