A non-destructive method for determination of composition and thickness of ternary alloy thin film by using the technique of X-ray fluorescence spectroscopy is employed in this paper. In this method, it is not necessary to prepare any similar solid or pure elemental standards, instead, the filter disk standards are used. These disk standards can be made readily and are stable for long period of time. A set of equations relating the characteristic X-ray intensities from elements in the film and its surface densities are formulated and solved for film composition. The quantitative dependence of attenuation of characteristic X-ray intensities of elements in substrate on increasing film thickness is used to determine the thickness. This method can be used to measure the film composition and thickness simultaneously.