The invention provides a high-refraction low-dispersion optical glass with low material cost, refractive index of 1.77-1.85, and Abbe number of 40-48, wherein the following components by weight percentage: 4-20% of SiO2, 8-24% of B2O3, 20-40% of La2O3, 11-30% of Gd2O3, 0-15% of Y2O3, 0-8% of TiO2, 0-8% of Ta2O5, more than 0 but less than or equal to 8% of Nb2O5, less than 1 of Ta2O5/Nb2O5, more than 0 but less than or equal to 15% of ZrO2, and 11-30% of ZnO. The invention reduces the content of Ta2O5 and optimizes the cost of raw materials; through rational composition design, the optical glass of the invention is conducive to precision molding while achieving the required optical constant, with excellent chemical stability. A glass preform and an optical element made of the optical glass are also disclosed.