  X-ray flares are generally supposed to be produced by the later central
engine activities, and may share the similar physical origin with prompt
emission of gamma-ray bursts (GRBs). In this paper, we have analyzed all
significant X-ray flares from the GRBs observed by {\em Swift} from April 2005
to March 2015. The catalog contains 468 bright X-ray flares, including 200
flares with redshifts. We obtain the fitting results of X-ray flares, such as
start time, peak time, duration, peak flux, fluence, peak luminosity, and mean
luminosity. The peak luminosity decreases with peak time, following a power-law
behavior $L_p \propto T_{peak,z}^{-1.27}$. The flare duration increases with
peak time. The 0.3-10 keV isotropic energy of X-ray flares distribution is a
lognormal peaked at $10^{51.2}$ erg. We also study the frequency distributions
of flare parameters, including energies, durations, peak fluxes, rise times,
decay times and waiting times. Power-law distributions of energies, durations,
peak fluxes, and waiting times are found in GRB X-ray flares and solar flares.
These distributions could be well explained by a fractal-diffusive,
self-organized criticality model. Some theoretical models basing on magnetic
reconnection have been proposed to explain X-ray flares. Our result shows that
the relativistic jets of GRBs may be Poynting-flux dominated.
