  The LAMOST spectra and $\it{Kepler}$ light curves are combined to investigate
the detached eclipsing binary KIC 8098300, which shows the O'Connell effect
caused by spot/facula modulation. The radial velocity (RV) measurements are
derived by using the tomographic spectra disentangling technology. The mass
ratio $q = K_1/K_2 = 0.812 \pm 0.007$, and the orbital semi-major axis
$a\mathrm{\sin}i = 14.984 \pm 0.048\ R_\odot$ are obtained by fitting the RV
curves. We optimize the binary model concerning the spot/facula activity with
the code PHOEBE and obtain precise parameters of the orbit including the
eccentricity $e=0.0217 \pm 0.0008$, the inclination $i=87.71\pm 0.04^\circ$,
and the angle of periastron $\omega=284.1\pm 0.5^\circ$. The masses and radii
of the primary and secondary star are determined as $M_1=1.3467 \pm 0.0001\
M_\odot$, $R_1=1.569 \pm 0.003\ R_\odot$, and $M_2=1.0940 \pm 0.0001\ M_\odot$,
$R_2=1.078 \pm 0.002\ R_\odot$, respectively. The ratio of temperatures of the
two component stars is $r_{teff}=0.924 \pm 0.001$. We also obtain the
periastron precession speed of $0.000024\pm 0.000001\ \mathrm{d}\ cycle^{-1}$.
The residuals of out-of-eclipse are analyzed using the Auto-Correlation
Function (ACF) and the Discrete Fourier Transform (DFT). The spot/facula
activity is relatively weaker, but the lifetime is longer than that of most
single main sequence stars in the same temperature range. The average rotation
period of the spots $P_{rot}=4.32\ d$ is slightly longer than the orbital
period, which may be caused by either the migration of spots/faculae along the
longitude or the latitudinal differential rotation. The activity may be
spot-dominated for the secondary star and facula-dominated for the primary
star.
