  By combining spectra from the CALSPEC and NGSL, as well as spectroscopic data
from the LAMOST Data Release 7 (DR7), we have analyzed and corrected the
systematic errors of the Gaia DR3 BP/RP (XP) spectra. The errors depend on the
normalized spectral energy distribution (simplified by two independent
``colors'') and $G$ magnitude. Our corrections are applicable in the range of
approximately $-0.5<BP-RP<2$, $3<G<17.5$ and $E(B-V)<0.8$. To validate our
correction, we conduct independent tests by comparing with the MILES and LEMONY
spectra. The results demonstrate that the systematic errors of $BP-RP$ and $G$
have been effectively corrected, especially in the near ultraviolet. The
consistency between the corrected Gaia XP spectra and the MILES and LEMONY is
better than 2 per cent in the wavelength range of $336-400$\,nm and 1 per cent
in redder wavelengths. A global absolute calibration is also carried out by
comparing the synthetic Gaia photometry from the corrected XP spectra with the
corrected Gaia DR3 photometry. Our study opens up new possibilities for using
XP spectra in many fields. A Python package is publicly available to do the
corrections (https://doi.org/10.12149/101375 or
https://github.com/HiromonGON/GaiaXPcorrection).
