A X-ray fluorescence spectrometric method for the determination of Cl in geological samples was developed. Pressed power pellets were used for measurements. The dffects of backing and placing in Spectrum Room of the samples on measurements were discussed in details. The detection limits of this method is 12 μg/g for Cl. The results are in agreement with certified values with prescision of RSD fo Cl(n=12) 10%. Precision and accuracy test by standard sample at the national level is good.