The measurement of soft X-ray supper thin film by means of diffractometer is the most common method employed abroad

but usually is limited to double crystal or small angle diffractometer. This paper intruduce a method

which solved the problem of diffraction peak shift and diffraction curve lossing due to the locating error of the sample when the wide angle diffractometer is used at low angle range

so that the wide angle diffractometer can be used in the small angle range. The paper emphasizes the analyses of the measurement results and the corparison of the experimental and theoretiod results

based on the calculating period of multilayered coatings and the thickness of single layer coatings. The measurement results of the thickness by means of wide angle diffraction are very believable and reliable. At present

the equipment for reflectance measurement in the soft X-ray spectral range has not been developed perfectly

the measurement of soft X-ray supper thin film by means of X-ray diffractometer seems to be more important.