The invention relates to optical glass and a preparation method thereof. The optical glass is prepared from the following components in percentage by weight: 10-21% of P2O5, 10-50% of Bi2O3, 0-50% ofNb2O5, 0-20% of TiO2, 0-12% of WO3, 0-6% of SiO2, 0-6% of B2O3, 0 -6% of Li2O, 0-4% of Na2O, 0-6% of K2O, 0-4% of Al2O3, 0-3% of ZrO2, 0-5% of CaO, 0-5% of ZnO, 0-30% of Ba0, 0-2% of MgO, 0-3% of SrOand 0-0.1% of Sb2O3. The optical glass has the advantages of being excellent in performance, high in refractive index, high in dispersion and capable of decreasing the number of lens, prisms and otheroptical elements used in an optical system, and therefore the requirements of light weight and miniaturization of the overall optical system are met.