The stochastic resonance (SR) of two-dimensional Duffing oscillator is studied in this paper. We propose the generalized parameter-adjustment SR of Duffing oscillator. On the basis of Kramers rate, we build a discrimination function of the SR of Duffing oscillator, and we expound the generalized parameter-adjustment SR laws of Duffing oscillator under different noise intensity and signal frequency conditions. The general method of generating the generalized parameter-adjustment SR of Duffing oscillator is also given in this paper.