The invention relates to a method for reducing calcined magnesite by using calcium carbide under normal pressure, which belongs to the field of nonferrous metal metallurgy. The method is characterized in that: the calcium carbide serving as a reducing agent, silicon dioxide serving as an additive, and the calcined magnesite (MgO) serving as a raw material are reacted in the presence of a small amount of calcium fluoride serving as a catalyst so as to produce magnesium vapor. The average grain size of reactants is about 100 meshes; and the actual ratio of the calcium carbide to the silicon dioxide to the magnesium oxide is (1-1.5):(0.75-1):1, and the calcium fluoride is 7 to 10 percent based on the total weight of the reactants. Material pellets with the diameter of about 3cm are prepared under the briquetting pressure of 30 to 50MPa and fed into a reactor; a reaction system does not contact air, and the inside of the reaction system is maintained in a normal pressure state; reaction is performed at the temperature of between 1,150 and 1,250 DEG C for 6 to 8 hours; and the magnesium vapor is finally introduced into a condenser so as to form crystal magnesium by condensation. A continuous reaction can be realized by the method and the process, so that production cost is greatly lowered, and the production cycle is shortened.