The binding energy of a hydrogenic impurity in self-assembled double quantum dots was calculated via the finite-difference method. The variation of the binding energy with stricture param- eters, the donor position and external magnetic field were studied in detail. The results show that the binding energy has a complex behavior due to the coupling between the two dots; it is much larger when the donor placed in the center of one dot than in the other positions; and the external magnetic field has different effects on the binding energy for different quantum dot size or lateral confinement.