As rapid advance in the laser and the laser technology, more and more lasers have been used in different application fields, which have different demands to the energy distribution of the laser spot. Flat-topped light beam is a type of beam with uniform radiance, so it has been widely applied in all kinds of field such as the material processing. The current research on the flat-topped beam mainly focused on how to obtain the beam and its propagation properties. In this paper, four experimental methods on how to obtain the flat-topped beam are summarized, among of which the beam shaping is emphatically introduced, and their advantages and disadvantages are analyzed. Then, four mathematical and physical models are represented and their field distributions expression and the characteristics are analyzed. The research on the partially coherent flat-topped beam is presented, and its propagation properties are compared with the coherent beam. Last, the applied prospects and the research directions on the flat-topped beam are forecasted.