An optical glass with high refractive index and low dispersion, having refractive index nd of 1.78-1.95, Abbe number vd of 32-50, and contains no GeO2, so it is not easily devitrified. An optical glass, represented by cation %, including: 1-20% of Si4+; 25-60% of B3+; 10-40% of La3+; 0-15% of Y3+; 0-20% of Nb5+; 0-15% of Ti4+; 0-10% of Ta5+; 0-5% of W6+; 0-15% of Zr4+; 0-10% of Zn2+; 0-10% of Bi3+. An optical glass with excellent transmittance, an optical glass preform and an optical element formed by the above optical glass. The optical element made by the above optical glass and the above glass preform or optical element blank, such as lens, can be used for optical systems.