The invention provides a light reinforced composite floating plate for preventing the water level from evaporating. The light reinforced composite floating plate for preventing the water level from evaporating comprises the following steps of: clipping a bidirectional plastic geogrid of 25-50KN into meshes with equal size, and adding benzene particles into cement mud, wherein the volume of benzene particles per cubic is 0.845-0.850m<3>; prefabricating method: pouring benzene particle mixed materials into a mold, filling to 1-2cm, compacting, then laying geogrid meshes at the lower layer, adding benzene particle mixed materials, filling to 5-9cm, compacting, laying geogrid meshes at the upper layer, then adding benzene particle mixed materials to 1-2cm, and compacting, thereby obtaining a mixed condensed plate, then demolding, brushing mud, bonding carbon fiber cloth, wrapping, and sealing, thereby preparing a stormy-wave-resistant, collision-resistant, seepage-resistant, ultraviolet-resistant, antifreezing and water-erosion-resistant performance light reinforced composite floating plate. When the plate is used, the plate is laid freely according the water area, and is not required to be connected and fixed.