Monolayer Ag In Te Sb O thin films were deposited by reactive RF sputtering using Ag In Te Sb alloy target in a mixture of argon oxygen plasma with different ratio of oxygen to argon. The reflectance spectra and optical constants of the films were studied. It was found that films deposited at P O 2 /P Ar  of 2%～4% had comparatively large reflectivity, after annealing at 300℃ under protection of argon for 30 minutes, the reflectivity in the wavelength range of 500～700 nm could rise by about 17%～25%; Film deposited at P O 2 /P Ar  of 2% had large absorption in the wavelength range of 400～650 nm, the optical constants (n,k) also changed much after annealing. The reflectivity contrast can be as high as 20% after being recorded using short wavelength laser (514 4 nm) with low power (10 mW) and short pulse width (100 ns). The films had good writing sensitivity and certain erasability. The XRD analyses indicated that only Sb crystal formed after annealing, as was different to crystallization characters of Ag-In-Te-Sb films. Components and chemical states of the filmwerean alyzed by XPS. This kind of films had the potential fo rusein high density optical storage.