Based on the analytical solution to quantum confinement states in one-dimensional crystals with asymmetric potentials, it is shown that the confined states within the energy bands of asymmetric quantum well (AQW)have potentials to be sources of THz radiation. The calculation demonstrates that it is the band mixture effectof AQW that makes the energy separation variable to favour THz emission. Compared with single the quantumwell with symmetric potentials, the electronic structure of AQW makes it a desirable source of THz emission.