  Previous MHD simulations have shown that wind must exist in black hole hot
accretion flows. In this paper, we continue our study by investigating the
detailed properties of wind, such as mass flux and poloidal speed, and the
mechanism of wind production. For this aim, we make use of a three dimensional
GRMHD simulation of hot accretion flows around a Schwarzschild black hole. The
simulation is designed so that the magnetic flux is not accumulated
significantly around the black hole. To distinguish real wind from turbulent
outflows, we track the trajectories of the virtual Largrangian particles from
simulation data. We find two types of real outflows, i.e., a quasi-relativistic
jet close to the axis and a sub-relativistic wind subtending a much larger
solid angle. Most of the wind originates from the surface layer of the
accretion flow. The poloidal wind speed almost remains constant once they are
produced, but the flux-weighted wind speed roughly follows $v_{\rm p,
wind}(r)\approx 0.25 v_k(r)$. The mass flux of jet is much lower but the speed
is much higher, $v_{\rm p,jet}\sim (0.3-0.4) c$. Consequently, both the energy
and momentum fluxes of the wind are much larger than those of the jet. We find
that the wind is produced and accelerated primarily by the combination of
centrifugal force and magnetic pressure gradient, while the jet is mainly
accelerated by magnetic pressure gradient. Finally, we find that the wind
production efficiency $\epsilon_{\rm wind}\equiv\dot{E}_{\rm wind}/\dot{M}_{\rm
BH}c^2\sim 1/1000$, in good agreement with the value required from large-scale
galaxy simulations with AGN feedback.
