  (abridged) We study the young stellar system GW Ori, concentrating on its
accretion/wind activity by using our high-resolution optical spectra and
$U$-band photometry. We also characterize the disk properties of GW Ori by
modeling its spectral energy distribution (SED). By comparing our data to the
synthetical spectra, we classify GW Ori as a G8 star. Based on the RVs derived
from the spectra, we confirm the previous result as a close companion in GW Ori
with a period of ~242 days and an orbital semi-major axis of ~1 AU. The RV
residuals after the subtraction of the orbital solution with the equivalent
widths of accretion-related emission lines vary with periods of 5-6.7 days
during short time intervals, which are caused by the rotational modulation. The
H$\alpha$ and H$\beta$ line profiles of GW Ori can be decomposed in two
central-peaked emission components and one blue-shifted absorption component.
The absorption components are due to a disk wind modulated by the orbital
motion of the close companion. Therefore, the systems like GW Ori can be used
to study the extent of disk winds. We find that the accretion rates of GW Ori
are rather constant but can occasionally be enhanced by a factor of 2-3. We
reproduce the SED of GW Ori by using disk models with gaps ~25-55 AU in size. A
small population of tiny dust particles within the gap produces the excess
emission at near-infrared bands and the strong and sharp silicate feature at 10
$\mu$m. The SED of GW Ori exhibits dramatic changes on timescales of ~20 yr in
the near-infrared bands, which can be explained as the change in the amount and
distribution of small dust grains in the gap. We collect a sample of
binary/multiple systems with disks in the literature and find a strong positive
correlation between their gap sizes and separations from the primaries to
companions, which is generally consistent with the prediction from the theory.
