Lanthanum titanate (H4) films were deposited by the thermal vapor deposition technique. After irradiating with a 1 064 nm and 532 nm lasers, the refractive index, extinction coefficient, Laser-Induced Damage Threshold (LIDT) of the films and damaging process of the films were investigated. The results showed that the refractive index of H4 films slightly increased after laser irradiating. The LIDT increased from 10.2 J/cm2 to 15.7 J/cm2 (5-pulse irradiation) after irradiating by using a 1 064 nm laser, however, the change of LIDT of the films was unobvious after irradiating by using a 532 nm laser. For the same sample, the LIDT which measured with a 1 064 nm laser was higher than that with a 532 nm laser. H4 film′s damage process underwent a slow 4-stage, slight, mild, moderate and extreme damage by using a 1 064 nm laser, whereas the damage process was a sudden change by using a 532 nm laser, underwent a 2-stage, moderate and extreme damage..