Disclosed is a method for evaporating and dehydrating a solid material; the method comprises: providing a plurality of digesters, with the digesters being in a parallel connection with respect to the flow direction of the solid material, wherein each digester repeatedly performs the arranged steps of step-by-step heating and evaporating and dehydrating the solid material from low temperatures to high temperatures in a time sequence. The solid material is brown coal. The quality of the brown coal is improved by the method.