Abstract: To study the deformation of optical surface when optical components deposited with high power laser films are exposed to room air, theoretical analysis was carried out to make clear that water-induced stress is and it is the main reason to cause such optical surface deformation including two formation mechanism: physical mechanism and chemical mechanism. A series of experiments were designed to investigate the transformation tendency of film stress, and the deformation was found with aging effect and humidity effect during storage. Which corresponding to the chemical mechanism and physical mechanism respectively.