  The spectra of emission-line galaxies (ELGs) from the extended Baryon
Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digit Sky Survey (SDSS)
are used to study the mass-metallicity relation (MZR) at $z\sim0.8$. The
selected sample contains about 180,000 massive star-forming galaxies with $0.6
< z < 1.05$ and $9 < {\rm log}(M_{\star}/M_{\odot}) < 12$. The spectra are
stacked in bins of different parameters including redshift, stellar mass, star
formation rate (SFR), specific star formation rate (sSFR), half-light radius,
mass density, and optical color. The average MZR at $z\sim0.83$ has a downward
evolution in the MZR from local to high-redshift universe, which is consistent
with previous works. At a specified stellar mass, galaxies with higher SFR/sSFR
and larger half-light radius have systematically lower metallicity. This
behavior is reversed for galaxies with larger mass density and optical color.
Among the above physical parameters, the MZR has the most significant
dependency on SFR. Our galaxy sample at $0.6<z<1.05$ approximately follows the
fundamental metallicity relation (FMR) in the local universe, although the
sample inhomogeneity and incompleteness might have effect on our MZR and FMR.
