The invention discloses pressure resistant plate glass and a preparation method thereof. The preparation method comprises the following steps: 1) subjecting metavanadate, borax, soluble carbonates and water to hydrothermal reaction under alkaline conditions, then filtering the reaction liquid and taking a filter cake to prepare an active composition; 2) mixing quartz sand, sodium carbonate, calcite, barite, sodium nitrate, zinc oxide and the active composition and then carrying out first fusion and then carrying out first cooling to prepare a cooling product; and 3) mixing expanded vermiculite, manganese dioxide, rare earth oxides and the cooling product and then carrying out second fusion and then carrying out second cooling to prepare the pressure resistant plate glass. The plate glass prepared by the method has excellent mechanical strength. Meanwhile, the method is accessible in raw materials and simple in processes.