The influence of Al/(Al+Si) molar ratio on the short-/mid-range structure and elastic modulus of alkali aluminosilicate glass was investigated via molecular dynamics simulation. The results show that the non-bridging oxygen in the glass network transforms to bridging oxygen and triple-bonded oxygen as the ratio of Al/(Al+Si) increases. When the ratio of Al/(Al+Si)>0.3, the non-bridging oxygen mainly changes to triple bond oxygen. The structural units transform to a high degree of polymerization, the connectivity of the glass network increases, and the elastic modulus of the glass increases as the ratio of Al/(Al+Si) increases. The elastic modulus of glass increases with the increase of Al/(Al+Si) molar ratio. The data calculated by the simulation are consistent with the experimental results, thus verifying a feasibility of using the molecular dynamics simulation to improve the glass composition.