The invention provides optical glass, a preformed blank using the glass and an optical element. The optical glass has a refractive index (nd) and an Abbe number (vd) within an expected range. Meanwhile, the partial chromatic dispersion rate (theta g, F) of the optical glass is small and the transparency of the visible light is improved. The optical glass comprises SiO2 components and more than one component selected from a group formed by the Ta2O5 component, Nb2O5 component, Na2O component and BaO component. A relationship is existent between the partial chromatic dispersion rate (theta g, F) and the Abbe number (vd). Specifically, when the Abbe number (vd) is no more than 25, then the partial chromatic dispersion rate (theta g, F) ranges between (-0.00160*vd plus 0.63460) and (-0.00563*vd plus 0.75573). When the Abbe number (vd) is larger than 25, the partial chromatic dispersion rate (theta g, F) then ranges between (-0.00250*vd plus 0.65710) and (-0.00340*vd plus 0.70000).