The XRD-Rietveld full-spectrum fitting method (Rietveld method) is an advanced technical method that is widely used in the field of materials science to solve the quantification issue of multiphase mixture samples. Theoretically, the Rietveld method could be applied in the geosciences field, and it can help geologists to get a better result in the analysis of mineral quantification of geoscience samples. However, in practical applications, there are several basic problems needing to be solved, especially concerning the applicability of the method itself and the reliability of analysis data. Regarding to these issues, taking soil samples for example, a simulation experiment was conducted in this study. Prior to application of the Rietveld method, three sets of simulated soil samples were prepared firstly according to the common knowledge of natural soil mineralogy, including quartz+hematite 1∶1 mixture sample, quartz+kaolinite 1∶1 mixture sample and quartz+kaolinite+montmorillonite 1∶1∶1 mixture sample. Using the Rietveld method, we obtained good XRD fitting lines for all simulated soil samples. Specifically, some important indices, including fitting value (Rwp<15%), fitting expectation (Rexp<15%) and goodness of fit (gof<5), could all meet the requirements of applying the Rietveld method. Also, the Rietveld-based mineral quantification data were very close to their real values, with errors only 0.63%, 1.46% and 1.03% for three samples respectively. This result indicated that the application of Rietveld method to quantify the soil mineral composition is feasible and reliable, which can get better results than the traditional “internal standard” method.