The internal standard and G-factor methods were applied to Rietveld X-ray diffraction quantitative analysis of Portland cement using XPert Highscore Plus and GSAS-EXPGUI software.The phase content of Portland cement was derived from Rietveld refined scale factor, calculated diffractometer constant and the mass attenuation coefficients by G-factor method.And the quantitative result from G-factor method was compared by internal standard methodology which was employed by separately adding 20% and 50% (weight percentage) of SiO2 as internal standard.The results show that the quantitation of Portland cement obtained by both of the above independent methods are almost consistent.And the absolute errors of phase content between these two methods are small.The absolute errors of most crystals are less than 1% in quantitative compare except C4AF,which is 1.2%, while the amorphous determination has the absolute error of 2.1%.