When a cement company used X-ray fluorescence analyzer to detect SiO2, CaO and other components of raw material samples, the detection data frequently exceeded the error phenomenon. The factors that may cause the error of X-ray fluorescence analyzer test data were analyzed, and the effects of operation error and instrument error were excluded in the test. It was found that the main reason for the error of test data was the poor repeatability of sample preparation method. The factors affecting sample preparation were further investigated, and the influence of particle effect on the error of test data was determined. By grinding the sample to pass the 0.08mm square screen, the problem of X-ray fluorescence analyzer was solved and the quality of clinker was improved.