In this article, the no-standards quantitative analysis method using the ratios of the X-ray intensities of the elements in the samples has been improved. The "full diffusion" model of the electron scattering has been properly modified and simplified and a stepped depth distribution curve of the X ray has been obtained. From this distribution curve, the quantitative relationship between the constituents of samples and the intensities of the characteristic X-rays has been determined. The analysed values of the Cu-Si, FeS2 NaCl and GaAs are coincident with the actual values. Our results are better in some extent than the results of Russ's method which used the calculated X-ray intensity factors of pure elements and the routine ZAF correction. The calculation procedure of our method is also simpler than the procedure of the latter method.