Based on the dielectric continuum model, we have studied the electron-optical phonon scattering rates in GaAs/Al xGa 1-xAs quantum wells with different structure parameters. It was found that the scattering rate of the symmetric interface phonon mode has a stronger dependence on the Al composition in the barriers than that of the confined mode. The effective phonon energy emitted by hot electrons in GaAs/Al xGa 1-xAs quantum wells with various Al compositions was estimated and the calculated value agrees with the experimental results qualitatively. For the dependence on the well width, scattering rates of the S+ mode drop considerably as the well width is increased. The dependence of the electron-optical phonon interaction on structure parameters can be clearly explained by the H and G factors defined in the article.