A high-modulus glass fiber composition includes the following components with corresponding amounts by weight percentage: 42-56.8% of SiO2, 15.8-24% of Al2O3, 9.2-18% of MgO, 0.1-6.5% of CaO, greater than 8% and less than or equal to 20% of Y2O3, 0.01-4% of TiO2, 0.01-1.5% of Fe2O3, 0.01-1.5% of Na2O, 0-1.5% of K2O, 0-0.7% of Li2O, 0-3% of SrO, 0-2.9% of La2O3. A total weight percentage of the above components is greater than or equal to 98%, and a weight percentage ratio C1=Y2O3/CaO is greater than or equal to 2.1.