This paper treats theoretically the angle dependence of the ground state binding energy of a shallow donor impurity in semiconductor quantum-well systems on the tilted magnetic field. By making an appropriate coordinate transform we have calculated the ground state binding energy of a shallow donor, impurity at the center of GaAs/Ga1-xAlxAs quantum well in the effective-mass approximations and variationally. We show that the binding energy depends strongly not only on quantum confinement, but also on the direction of the magnetic field. For example; for L-0 = 100 Angstrom, the change of the binding energy between theta = 15 and 45degrees approximately is 2.5R(y) (similar to 13 meV). We expect that this change will be useful in designing the quantum-well structure in which the impurity effects play important role. (C) 2003 Elsevier Science Ltd. All rights reserved.