We present an improved radiative pumping model for interstellar H2O and OH masers. This overcomes the defects of former radiative models, and is compatible with astronomical conditions. For the regions of strong H2 O and OH formation, it is shown that the rotational population is affected by collisions less than by radiation.A reasonable scheme for both regeneration and destruction of interstellar H2 O and OH molecules is investigated.It can close the dynamical cycle of interstellar HaO and OH species, and can give an appropriate interpretation for both interstellar H2 O and OH masers. This model has been confirmed by experiments.