  X-ray flares have routinely been observed from the supermassive black hole,
Sagittarius A$^\star$ (Sgr A$^\star$), at our Galactic center. The nature of
these flares remains largely unclear, despite of many theoretical models. In
this paper, we study the statistical properties of the Sgr A$^\star$ X-ray
flares, by fitting the count rate (CR) distribution and the structure function
(SF) of the light curve with a Markov Chain Monte Carlo (MCMC) method. With the
3 million second \textit{Chandra} observations accumulated in the Sgr A$^\star$
X-ray Visionary Project, we construct the theoretical light curves through
Monte Carlo simulations. We find that the $2-8$ keV X-ray light curve can be
decomposed into a quiescent component with a constant count rate of
$\sim6\times10^{-3}~$count s$^{-1}$ and a flare component with a power-law
fluence distribution $dN/dE\propto E^{-\alpha_{\rm E}}$ with $\alpha_{\rm
E}=1.65\pm0.17$. The duration-fluence correlation can also be modelled as a
power-law $T\propto E^{\alpha_{\rm ET}}$ with $\alpha_{\rm ET} < 0.55$ ($95\%$
confidence). These statistical properties are consistent with the theoretical
prediction of the self-organized criticality (SOC) system with the spatial
dimension $S = 3$. We suggest that the X-ray flares represent plasmoid
ejections driven by magnetic reconnection (similar to solar flares) in the
accretion flow onto the black hole.
