The invention is about a sort of lightweight partition wall board. It is made from magnesium oxide, magnesium chloride, dry rock powder, flyash, French chalk, high alumina cement, ferrous sulfate, tertiary sodum phosphate, phosphoric acid solution and sawdust. The lightweight partition wall board has the following advantage: the fist, it can save energy, reduce cost and have no pollution. The second, the board has fine intensity, good water resistance and resistance to aging. The third, it has small shrinkage, get over the problem that appear when the boards join. The fourth, the partition wall board no longer distort for using inorganic material and controlling the quality of material. Lastly, it has good shock resistance, waterproof, fire resistance, soundproofing and it get over the partition wall board to be yellow.