Even though there have been extensive studies on the local in time well-posedness theory on the Prandtl equation and its related models, there are relatively less results on global in time existence. In this talk, after a brief review on the classical Prandtl equation, we will present a new approach to study this problem by considering other two physical models, that is, the MHD in the Hartmann regime and the hyperbolic version of anisotropic Navier-Stokes equations. The talk is based on some recent work with Wei-xi Li and Rui Xu.