In this paper, some variations of properties of the composite MoS2-LaF3 cosputtered films and the pure MoS2-sputtered films (as the composite films and the pure films respectively) after storage in moist air ( similar to 100% RH) were investigated. The orientation, surface structure and chemical state of the films were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The tribological properties of the films were investigated in vacuum ( approximate to 0.77 mPa) and in air (11-15 degrees C, 35-45% RH). The results showed that the composite films have a longer wear life and more stable friction coefficient than the pure films after storage in moist air for a period of time, which is due to the more suitable orientation and more dense stable structure of the former. The dense stable structure of the composite film restricts deep oxidation of MoS2 and prevents corrosion of the substrate.