The second-harmonic generation(SHG) susceptibility of a wurtzite GaN/InxGa1-xN coupling quantum well(CQW) with strong built-in electric field was theoretically investigated.The calculated results reveal that the resonant SHG coefficients reach the order of magnitude of 10-7 m/V and the SHG coefficients are not monotonic functions of the well width,barrier width and the doped concentration of the CQW systems.Our results also show that a strong SHG coefficient can be obtained in the nitride CQW by choosing optimized structural parameters and doped fraction.