The embodiment of the invention discloses a preparation method of lithium metasilicate glass ceramic, comprising the following steps: (a) preparing matrix molten glass; (b) pouring the matrix molten glass into a mould, and cooling to obtain a matrix glass body; and (c) placing the matrix glass body into a heating device, and carrying out heat treatment. According to the heat treatment, temperature rises at the heating rate of 5-20 DEG C / min to 450-600 DEG C, and thermal insulation is carried out for 20-150 min. After the heat treatment, furnace cooling is conducted to obtain the lithium metasilicate glass ceramic. In comparison with the prior art, the technical scheme has the following advantages: in the obtained lithium metasilicate glass ceramic, crystal morphology of the main crystalline phase lithium metasilicate is nanoscale and the crystal morphology is uniform spheres. Crystallization degree is low. Thus, hardness of lithium metasilicate glass ceramic is reduced. Abrasion to cutting needles or grinding tools can be reduced during the machining process, and the whole processing time is shortened.