In this paper

the W/B4C periodic multilayer films are designed

and their optical characters （reflectivity） are calculated based on the Fresnel formula connected with the Nevot-Croce model. The W/B4C X-ray periodic multilayer films with small period （d=4.2nm） are fabricated by the high vacuum magnetron sputtering technology

and its structure was measured by D1 XRD from BEDE Company

UK. On the Beijing Synchrotron Radiation X-ray Fluorescence Analysis Spectroscopy （XFAS） beam line

the W/B4C multilayer film was used as the monochromator instead of the crystal for the XFAS experiment. The experiment results demonstrated that the quasi-monochromatic X-ray beam can be obtained by using such period multilayer film. The EFAS experiment of standard sample Nist

6

12 proves that the tiny content element （about 50 μg/g） can be probed by the new XFAS optical setup based on W/B4C periodic multilayer film.