In order to quickly and accurately test and identify the residual paper ashes on the scene of the case, 32 paper ashes from different sources and uses were determined by X-ray fluorescence spectrometry combined with system clustering and principal component analysis of multivariate statistics. Theoretical analysis and experimental verification were then carried out. The results show that the samples can be distinguished accurately according to the types and contents of the elements in the samples. At the same time, 32 samples are divided into five categories, and the classification results of the two methods are basically the same. The cumulative variance contribution rate of PC2 is as high as 99.86%. This research method does not destroy the sample, has good reproducibility, and the results are scientific and ideal, which provides a theoretical basis for the examination of trace evidence.