The invention discloses paramagnetic faraday rotator glass and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing tetraterbium heptaoxide, boric acid, aluminium oxide, ammonium dihydrogen phosphate, antimony oxide and silicon carbide so as to obtain mixed batch; and then melting the mixed batch into molten glass at a high temperature in air atmosphere, finally pouring the molten glass into a stainless steel mold for forming, and precisely annealing so as to obtain the paramagnetic faraday rotator glass. The preparation method has the advantages that through the oxidation-reduction characteristic of the mixed batch, the low valence of rare earth ions in the glass is ensured, a platinum crucible is protected from corrosion, and platinum ions are prevented from entering the glass. The optical quality of the paramagnetic faraday rotator glass is improved; a founding technology of the paramagnetic faraday rotator glass is improved and simplified. The prepared paramagnetic faraday rotator glass is high in rare earth content, low in rare earth ion valence, high in Verdet constant, high in light transmittance, absorption-free in a visible light range, simple in preparation technology and operational operation and suitable for industrial production.