  Cassiopeia A (Cas A) as the nearby young remnant of a core-collapse supernova
is the best candidate for astrophysical studies in supernova explosion and its
environment. We studied hard X-ray emissions from Cas A using the ten-year data
of INTEGRAL observations, and first detected non-thermal continuum emission
from the source up to 220 keV. The $^{44}$Ti line emissions at 68 and 78 keV
are confirmed by our observations with a mean flux of $\sim (2.2\pm 0.4)\times
10^{-5}$ ph cm$^{-2}$ s$^{-1}$, corresponding to a $^{44}$Ti yield in Cas A of
$(1.3\pm 0.4)\times 10^{-4}$ \ms. The continuum emission from 3 -- 500 keV can
be fitted with a thermal bremsstrahlung of $kT\sim 0.79\pm 0.08$ keV plus a
power-law model of $\Gamma \sim 3.13\pm 0.03$. The non-thermal emission from
Cas A is well fitted with a power-law model without a cutoff up to 220 keV.
This radiation characteristic is inconsistent with the diffusive shock
acceleration models with the remnant shock velocity of only 5000km s$^{-1}$.
The central compact object in Cas A cannot contribute to the emission above 80
keV significantly. Some possible physical origins of the non-thermal emission
above 80 keV from the remnant shock are discussed. We deduce that the
asymmetrical supernova explosion scenario of Cas A is a promising scenario to
produce high energy synchrotron radiation photons, where a part of ejecta with
the velocity of $\sim 0.1c$ and opening angle of $\sim10^\circ$ can account for
the 100-keV emission, consistent with the "jet" observed in Cas A.
