  We previously built a sample of 14,012 extremely variable quasars (EVQs)
based on SDSS and Pan-STARRS1 photometric observations. In this work we present
the spectral fitting to their SDSS spectra, and study the spectral variation in
1,259 EVQs with multi-epoch SDSS spectra (after prudently excluding spectra
with potentially unreliable spectroscopic photometry). We find clear
"bluer-when-brighter" trend in EVQs, consistent with previous findings of
normal quasars and AGNs. We detect significant intrinsic Baldwin effect (iBeff,
i.e., smaller line EW at higher continuum flux in individual AGNs) in the broad
MgII and CIV lines of EVQs. Meanwhile, no systematical iBeff is found for the
broad Hb line, which could be attributed to strong host contamination at longer
wavelengths. Remarkably, by comparing the iBeff slope of EVQs with archived
changing-look quasars (CLQs), we show that the CLQs identified in literature
are mostly likely a biased (due to its definition) sub-population of EVQs,
rather than a distinct population of quasars. We also found no significant
broad line breathing of either Hb, MgII or CIV, suggesting the broad line
breathing in quasars may disappear at longer timescales ($\sim$ 3000 days).
