Raman scattering of diamond films prepared by hot filament CVD method has been measured. Raman spectra (1100-1800 cm-1) of diamond films were fitted by using a nonlinear least squares method with several lineshape functions. The best fit model was obtained which indicates that 1355 cm-1 peak for graphite D-band is an indispensable component of Raman structure of diamond films. The calculated curves agree well with the experimental Raman data. Moreover, with consideration of both graphite D-band and spatial line shape of Raman peak in diamond area can be explained. With further analysis of fitted parameters, quality of diamond crystalline and diamond content in diamond films can be shown. Good results in fitting several Raman spectra of diamond films indicate that the new fitting model is applicable.