The author put forward that the change of the electron clouds of the transition metal ions is the electron pairing medium in unconventional superconductors. It is just like the vibration of lattice is the electron pairing medium in conventional superconductors. Calculations with TDDFT method show that the frequency of the change of the electron clouds of the transition metal ions is close to that of the lattice. So, the change of the electron clouds can be excited by free electrons. Results of three copper oxide superconductors show that the higher the frequency, the higher the transition temperature. The difference between the change of the electron clouds and the lattice is also presented. The difference can explain special properties of unconventional superconductors, such as real space paring, pseudo energy gap, d symmetry and unconventional isotopy effect.