  AT2019wey is a new galactic X-ray binary that was first discovered as an
optical transient by the Australia Telescope Large Area Survey (ATLAS) on
December 7, 2019. AT2019wey consists of a black hole candidate as well as a
low-mass companion star ($M_{\text {star }} \lesssim 0.8 M_{\odot}$) and is
likely to have a short orbital period ($P_{\text {orb }} \lesssim 8$ h).
Although AT2019wey began activation in the X-ray band during almost the entire
outburst on March 8, 2020, it did not enter the soft state during the entire
outburst. In this study, we present a detailed spectral analysis of AT2019wey
in the low/hard state during its X-ray outburst on the basis of Nuclear
Spectroscopic Telescope Array \emph observations. We obtain tight constraints
on several of its important physical parameters by applying the State-of-art
\texttt{relxill} relativistic reflection model family. In particular, we
determine that the measured inner radius of the accretion disk is most likely
to have extended to the innermost stable circular orbit (ISCO) radius, i.e.,
$R_{\text{in}}=1.38^{+0.23}_{-0.16}~R_{\text{ISCO}}$. Hence, assuming
$R_{\text{in}}$=$R_{\text{ISCO}}$, we find the spin of AT2019wey to be
$a_{*}\sim$ $0.97$, which is close to the extreme and an inner disk inclination
angle of ~$i\sim$ $22 ^{\circ}$. Additionally, according to our adopted models,
AT2019wey tends to have a relatively high iron abundance of
$A_{\mathrm{Fe}}\sim$ 5 $A_{\mathrm{Fe}, \odot}$ and a high disk ionization
state of $\log \xi\sim$ 3.4.
