Abstract: A lightweight high-strength ceramsite, comprising solid raw materials and activator as the raw materials, which can be respectively expressed in parts by weight, the solid raw materials: 100 parts, the activator: 1-15 parts; wherein said solid raw materials comprise fly ash: 100 parts, high-alumina fly ash, bauxite and red mud: 6-18 parts, silica fume: 1-5 parts, surfactant: 0.1-3 parts, plasticizer: 6-24 parts; and said activator comprises alkali metal hydroxide: 5-20 parts and alkali metal silicate: 80-95 parts. The lightweight high-strength ceramsite product prepared has a density level of 700-1100 kg/m3 and cylindrical compressive strength of 10-20 MPa, and thus is not susceptible to damage.