Tungsten silicide (WSix) films, deposited by chemical vapour deposition are normally amorphous in nature, and need to be annealed at high temperature to obtain low resistivity required for interconnections and metallization layers in VLSI circuits. In this paper, we focus on this annealing process for films deposited on Si and SiO2 substrate, and having Si/W ratio of 2.4. The characterization methods used were time-resolved X-ray diffraction, Resistivity measurement, and Rutherford backscattering spectroscopy analysis. We observe that 30 minutes is not sufficient for complete transformation of the WSi2.4 films on Si substrate. We also report on the dependence of annealing behaviour of nonstoichiometric WSixfilm on the substrate type.