The invention discloses high-strength lithium disilicate glass ceramic and a preparation method thereof. The glass ceramic comprises the following chemical components in percentage by weight: 59-80% of SiO2, 10-18% of Li2O, 0.1-14% of MgO, 0-15% of Al2O3, 1-8% of P2O5, 0-5% of Na2O, 0-7% of CaO, 0-9% of K2O, 0.5-8% of stabilizer and 0-10% of colorant, wherein the stabilizer is selected from one or more of ZrO2, SrO, BaO and Y2O3, and the colorant is selected from one or more of Eu2O3, CeO<+>, Tb4O7, La2O3, Ta2O5, MnO2 and Fe2O3. The lithium disilicate glass ceramic is a material which contains a residual glass phase, a Li2Si2O5 principal crystalline phase and a small quantity of Li3PO1, quartz, cristobalite, zirconium oxide or magnesium-aluminum silicate phase and is prepared by controlling nucleation and crystallization processes after carrying out heat treatment on lithium disilicate matrix glass. The lithium disilicate glass ceramic is very high in bending strength and fracture toughness and favorable in translucence and chemical stability and can serve as a full-ceramic dental material applied to the field of dental restoration.