  We aim to investigate the propriety of stellar parameter errors of the
official data release of the LAMOST low-resolution spectroscopy (LRS) survey.
We diagnose the errors of radial velocity (RV), atmospheric parameters ([Fe/H],
T eff , log g) and {\alpha}-enhancement ([{\alpha}/M]) for the latest data
release version of DR7, including 6,079,235 effective spectra of 4,546,803
stars. Based on the duplicate observational sample and comparing the deviation
of multiple measurements to their given errors, we find that, in general, the
error of [{\alpha}/M] is largely underestimated, and the error of radial
velocity is slightly overestimated. We define a correction factor k to quantify
these misestimations and correct the errors to be expressed as proper internal
uncertainties. Using this self-calibration technique, we find that the
k-factors significantly vary with the stellar spectral types and the spectral
signal-to-noise ratio (SNR). Particularly, we reveal a strange but evident
trend between k-factors and error themselves for all five stellar parameters.
Larger errors tend to have smaller k-factor values, i.e., they were more
overestimated. After the correction, we recreate and quantify the tight
correlations between SNR and errors, for all five parameters, while these
correlations have dependence on spectral types. It also suggests that the
parameter errors from each spectrum should be corrected individually. Finally,
we provide the error correction factors of each derived parameter of each
spectrum for the entire LAMOST-LRS DR7.
