  Accurate determination of stellar atmospheric parameters and elemental
abundances is crucial for Galactic archeology via large-scale spectroscopic
surveys. In this paper, we estimate stellar atmospheric parameters -- effective
temperature T_{\rm eff}, surface gravity log g and metallicity [Fe/H], absolute
magnitudes M_V and M_{Ks}, {\alpha}-element to metal (and iron) abundance ratio
[{\alpha}/M] (and [{\alpha}/Fe]), as well as carbon and nitrogen abundances
[C/H] and [N/H] from the LAMOST spectra with amultivariate regressionmethod
based on kernel-based principal component analysis, using stars in common with
other surveys (Hipparcos, Kepler, APOGEE) as training data sets. Both internal
and external examinations indicate that given a spectral signal-to-noise ratio
(SNR) better than 50, our method is capable of delivering stellar parameters
with a precision of ~100K for Teff, ~0.1 dex for log g, 0.3 -- 0.4mag for M_V
and M_{Ks}, 0.1 dex for [Fe/H], [C/H] and [N/H], and better than 0.05 dex for
[{\alpha}/M] ([{\alpha}/Fe]). The results are satisfactory even for a spectral
SNR of 20. The work presents first determinations of [C/H] and [N/H] abundances
from a vast data set of LAMOST, and, to our knowledge, the first reported
implementation of absolute magnitude estimation directly based on the observed
spectra. The derived stellar parameters for millions of stars from the LAMOST
surveys will be publicly available in the form of value-added catalogues.
