The energy of a hydrogenic impurity in GaN/Al_xGa_(1-x)N compositional parabolic quantum well(PQW) is investigated by variational method.The ground state,the binding energy of hydrogenic impurity as a function of the well width and the energy of hydrogenic impurity as a function of the magnetic field are given.The numerical results indicate that the influence of external magnetic field on the ground state and the binding energy of a hydrogenic impurity is obvious,and the influence increases with increasing well width.The bound degree of the GaN/Al_(0.3)Ga_(0.7)N PQW to the hydrogenic impurity is stronger than that of the GaAs/Al_(0.3)Ga_(0.7)As PQW.