The invention relates to a building material and a method for preparing the same, in particular to a glass fiber reinforced cement board and a method for preparing the same. The glass fiber reinforced cement board comprises the following components in weight portion: 100 portions of Portland cement, 13.6 to 15 portions of high alumina cement, 3.1 to 3.4 portions of fly ash, 5.7 to 6.3 percent of plaster stone powder, 120 to 132 portions of ceramsite, 6.5 to 7.1 percent of foaming agent, 74.5 to 81.3 percent of dispersing agent, 53 to 58.7 portions of pure water and 3.6 to 4 portions of plastic-coated glass fiber grid cloth. The preparation method sequentially comprises the following steps: mixing weighed-up solid materials, adding weighed-up liquid materials in the previous step, cavity forming, roll extruding, vibration, cutting and curing. The invention has the advantages that: the glass fiber reinforced cement board has advantages of light volume weight, high strength, low dry shrinkage wet swelling coefficient, no after expansion and shrinkage, corrosion resistance, sound insulation, heat insulation, fire resistance and non-combustion; the preparation method has the characteristics of scientific and reasonable method, continuous production, high efficiency and low cost, flat board surface, convenient in-site mounting and the like; the glass fiber reinforced cement board is good in water resistance, and particularly applied to the finishing of internal and external walls and ceilings of various buildings in wet environments; moreover, the glass fiber reinforced cement board and a method for preparing the same have the advantages of ensuring the strength and service life of cement due to the adoption of the plastic-coated anti-alkali glass fiber grid cloth, along with reasonable blending ratio and reduced alkalinity.