The invention relates to a method for preparing raw Pu'er tea from tea raw materials growing at low altitude. The method comprises withering, deactivation of enzymes, pile fermentation, re-deactivation of enzymes, re-fermentation of a pile, rolling and drying in the sun. According to the method, a temperature in deactivation of enzymes is in a range of 170-230 DEG C, total time of deactivation of enzymes is 70-130min, the rotation number of a machine of deactivation of enzymes is 2-4 r/min and the pile fermentation process is carried out at a high temperature. The method utilizes different pieces of tea or tea picked in different reasons as a raw material. The products in different batches have the same and stable quality the same to that of Yunnan raw Pu'er tea growing at high altitude. The method widens a Pu'er tea raw material resource, greatly improves a raw Pu'er tea yield and reduces a production cost.