Abstract: The characters of asymmetrical step wells are studied. The resonantly enhanced second- order susceptibilityχ(2)2ωis calculated, and the changes ofχ(2)2ωwith the width of the wells, the width and height of the step, the barrier width and the wave length of incident light are given. The obtained results provide a certain basis for optimizing the properties of second-harmonic producer, and developing new nonlinear optical materials.