The invention discloses high borosilicate glass and a preparation method thereof, and relates to the field of glass raw material production processes. The high borosilicate glass comprises the following raw materials in percentage by mass: 60 to 68% of SiO2, 13 to 16% of Na2O, 1.5 to 2.4% of Al2O3, 8.0 to 9.0% of CaO, 0.4 to 1.0% of BaO, 0.3 to 0.9% of B2O3, 0.1 to 0.25% of CeO2, and 8 to 10% of pyrophyllite. The method comprises the following steps: carrying out high-temperature melting in a melting furnace to obtain melting liquid, clarifying and homogenizing the melting liquid, and flowing the melt into a working pool to obtain a base material; guiding the base material into the forming groove to obtain a glass plate; feeding the glass plate into an annealing furnace for annealing treatment; and introducing hot air into the glass after the annealing treatment, and storing the glass subjected to ventilation and reshaping in a room-temperature, dry, windless and dustless environment. A proper amount of pyrophyllite is added into the high borosilicate glass raw material to replace a part of quartz sand, so that the production cost is effectively reduced on the basis of keeping the performance of the high borosilicate glass.