Transfer matrix method has been used to analyze Curie-temperature (TC) modulation by polarization-induced built-in electric fields in Mn δ-doped GaN/AlGaN quantum wells. Schrdinger equation is employed to calculate the quantum-confined subband energies and the distribution of their corresponding envelope fuctions. Based on these，we investigate the dependence of TC on the built-in electric fields in different structures of quantum well. By changing the asymmetry of double quantum wells (DQW)，TC can be raised up to 3 times.