We propose a method based on X-ray absorption spectra (XAS),which allows the calculation of each channel in the energy spectrum. The theoretical absorption energy spectrum of the sample is obtained using the attenuation coefficient curve of the sample elements and the background energy spectrum of the radiation source, and compares with the actual absorption energy spectrum of the sample. The energy spectrum is fitted and the element surface density is calculated with the annealing algorithm. The results show that the standard deviation of repeated experiments when measuring a single element is low and the measurement uncertainty is in the order of 10-4g/cm2. This system can also be used for the measurement of the areal density of multi-element thin films, meeting the requirements of non-destructive and highly stable measurements of metal thin films in inertial confinement fusion experiments.