Tungsten silicide films have been sputtered onto silicon substrate and annealed at temperature ranging from 400 to 1000℃ in vacuum. The structure and defect of each film is detected by X-ray diffraction (XRD) and positron annihilation technology (PAT), respectively. The sheet resistance has been measured and the result in-dicates that the sheet resistance of films decrease steeply as a result of annealing in the range of 600-700℃. This phenomenon corresponds to the crystallization of W5Ｓｉ3 tetragonal phase in films which has been certified by XRD. Electrical properties of films are sensitive to structure and defects in films and electrical measurement can be used as a good probe for the study on the characteristics of films.