Abstract: Accurate Measurement of the Concentrative Ratio of Uranium Isotopes by Mass SpectrometryTang Hansen(Jiangsu institute of Petrochemical Technology, Changzhou 213016, China)Abstract:In this paper it is discussed in detail how to accurately measure the concentrative ratio of UF, sample-pair with mass-spectrometric analysis. In order to lessen memory effect, the method of passivative treatment with fluorine can also be used in addition tothe usage of molecular beam inlet system. Indicated in this paper are system deviationssimmilar to memory effect due to secondary electron, tail of peak and formation of impure ions, and it is described how to measure, estimate and reduce these deviations. Itis also discussed the effect of sample purification and operating conditions and the random deviation of measurement. At last it is seen that with precision mass-spectrometerand the method mentioned above, the total relative deviation of measurement of samplepair with about 10% concentrative ratio could be less than 0. 4%. It is also given themethod of examination and rectification wyh standard-pair.Keywords: mass spectrometry, measurement, uranium isotope, concentrative ratio.