On the basis of interaction between layers, the physical model of the bilayer spherical namometric system have been worked out. With the Green function method and Fourier transform, the electronic potential energy has been figured out for the system. In the example of HgS/CdS spherical nanometric system, the effect of system size and the layers' mutual effect has been discussed in terms of the electronic potential energy. The results show that: the layers' mutual effect could make the average height of the electronic potential barrier of the spherical namometric system lower; the more the layers' mutual effect is, the lower the height of the electronic potential barrier is, and the greater the undulation of the electronic potential energy curve is. For the same layers' mutual effect, electronic ground state energy and revised energy by layers' mutual effect will be reduced with the increase of particle radius; but for the same size, the revised energy by layers' mutual effect will increase with the increase of the layers' mutual effect.