A glass composition for substrates having good polishability while securing characteristics for FPD substrates, especially for PDP substrates, from which a glass substrate having excellent polishing workability and productivity can be obtained, is provided.A glass composition for substrates, which is characterized by comprising, as represented by mass % based on oxides, from 55 to 75% of SiO2, from 5 to 15% of Al2O3, from 0 to 4% of MgO, more than 5.5% and at most 12% of CaO, from 5 to 18% of SrO, from 0 to 13% of BaO, from 0.5 to 6% of ZrO2, from 0 to 10% of Na2O, from 0 to 15% of K2O, from 6 to 20% of Na2O+K2O, from 17 to 25% of MgO+CaO+SrO+BaO, and from 15 to 25% of CaO+SrO, as a glass matrix composition; and having a glass transition point of at least 600° C., an average thermal expansion coefficient of from 75×10−7 to 90×10−7/° C. within a range of from 50 to 350° C., and an abrasion resistance of at least 98.