  The properties of the dusty tori in active galactic nuclei (AGNs) have been
investigated in detail, mainly focusing on the geometry and components;
however, the kinematics of the torus is still not clear. The narrow iron
K$\alpha$ line at 6.4 keV is thought to be produced by the X-ray reflection
from the torus. Thus, the velocity-resolved reverberation mapping of it is able
to constrain the kinematics of the torus. Such effort is limited by the
spectral resolution of current CCD detectors and should be possible with the
microcalorimeter on the next generation X-ray satellite. In this paper, we
first construct the response functions of the torus under a uniform inflow, a
Keplerian rotation, and a uniform outflow. Then the energy-dependent light
curve of the narrow iron K$\alpha$ line is simulated according to the
performance of the X-ray Integral Field Unit in Athena. Finally, the
energy-dependent cross-correlation function is calculated to reveal the
kinematic signal. According to our results, one hundred observations with 5 ks
exposure of each are sufficient to distinguish the above three velocity fields.
Although the real geometry and velocity field of the torus could be more
complex than we assumed, the present result proves the feasibility of the
velocity-resolved reverberation mapping of the narrow iron K$\alpha$ line. The
combination of the dynamics of the torus with those of the broad line region
and the host galaxy is instructive for the understanding of the feeding and
feedback process of AGNs.
