Abstract: In order to investigate the well and barrier width and the position of donors effect on the binding energies of shallow-donor impurities, the binding energy of the system in symmetrical GaAs-Ga_1-xAl_xAs double quantum wells are calculated by using a variational method within the effective-mass approximation. The results are in good agreement with recorded results. It is found that, the binding energy is close to those of the single well when the barrier width, increases, and the binding energy has a minimum when the barrier width gets smaller and smaller.