X-ray diffractometry is widely used for quality control and process control in cement. This article presents an accurate and precise quantification method for free lime in a clinker material and an accurate quantification method of the admixtures in a blended cement. The partial accumulation measurement was used to make a calibration curve including a scale factor to improve the accuracy and precision of the quantitative method. Analytical result of free lime showed good agreement with its preparation value and had a small standard deviation. The reference intensity ratio method combined with the WPPF method was applied to admixture quantification in a blended cement for accurate quantification. The quantitative values of the admixtures in the simulation sample with a three-component system showed good agreement with the preparation values.