The invention relates to a glass composition, a glass substrate and a chemical strengthening method thereof. The composition contains SiO2, Al2O3, K2O, Na2O, ZrO2 and B2O3, wherein relative to 100 parts by weight of SiO2, the Al2O3 content is 25-40 parts by weight, the K2O content is 1-9 parts by weight, the Na2O content is 15-40 parts by weight, the ZrO2 content is 0.05-3 parts by weight, and the B2O3 content is 1-15 parts by weight; and R is calculated to be 6.87-13.89 according to the formula below: R=0.206w(Al2O3)+0.17w(K2O)-0.006w(Na2O)+0.13w(ZrO2)+0.37w(B2O3).Since the disclosed composition has the defined specific components and content ranges thereof, glass prepared from the composition has high strain point and softening point and low melting temperature, has excellent chemical strengthening property, and can be used for preparing the chemically-strengthened glass substrate. The surface of the chemically-strengthened glass substrate prepared according to the method has high surface stress and hardness, so that the surface scratch resistance of the chemically-strengthened glass substrate is improved, thereby ensuring that the chemically-strengthened glass substrate can resist the effect of external forces such as fall, abrasion and the like.