Mechanical and thermoelastic charecteristics of optical films are important to ensure the performance of optical coating systems. SiO2 films were prepared by dual ion beam sputtering (DIBS) on Si <110> and Schott Q1. The mechanical and thermoelastic properties of films as-deposited and annealed were systematically investigated. The results show that reduced Young′s modulus (Er) is elevated to 72 GPa while the film was annealed at 750 ℃, and hardness (H) increases to over 10 GPa. The as-deposited films show compressive stress and the stress could be dramatically released while annealed over 450 ℃, incicating that heat treatment could improve the internal stress of SiO2 film. Poisson′s ratio (vf) of annealed SiO2 films is around 0.18, and Young′s modulus (Ef) of as-deposited and annealed films is larger than that of fused silica, and elevated over 50 GPa while annealed at 750 ℃. Thermal expansion coefficient (αf) decreases from 6.78×10-7 ℃-1 to the minimum value 5.22×10-7 ℃-1 while annealed at 550 ℃.