The invention provides a method and a device for pre-processing an X-ray fluorescence spectrum. The method comprises the following steps: acquiring target spectrum information of soil samples with preset number, wherein the target spectrum information is X-ray fluorescence spectrum information and comprises the absorbance of each wavelength; calculating ideal spectrum information according to eachabsorbance; calculating regression coefficient corresponding to each soil sample according to the ideal spectrum information and the target spectrum information of each soil sample; calculating the absorbance of each soil sample after correction according to the target spectrum information of each soil sample and the regression coefficient corresponding to each soil sample, and determining that the absorbance of each soil sample after correction is the target spectrum information of each soil sample after pre-processing. The X-ray fluorescence spectrum is pre-processed by the method providedby the invention, so that denoising of the spectrum, baseline drift and correction of light scattering can be realized, and the precision and the stability of modeling are improved conveniently.