  Changing-look active galactic nucleus NGC~4151, which has attracted a lot of
attention, is undergoing the second dramatic outburst stage in its evolutionary
history. To investigate the geometry and kinematics of the broad-line region
(BLR), and measure the mass of supermassive black hole in NGC~4151, we perform
a seven-month photometric and spectroscopic monitoring program in 2020--2021,
using the 2.4 m telescope at Lijiang Observatory. We successfully measure the
time lags of the responses from broad \ha, \hb, \hg, \hei, and \heii\ emission
lines to continuum variation, which are $7.63_{-2.62}^{+1.85}$,
$6.21_{-1.13}^{+1.41}$, $5.67_{-1.94}^{+1.65}$, $1.59_{-1.11}^{+0.86}$, and
$0.46_{-1.06}^{+1.22}$ days, respectively, following radial stratification. The
ratios of time lags among these lines are $1.23 : 1.00 : 0.91 : 0.26 : 0.07$.
We find that the continuum lag between the ultraviolet and optical bands can
significantly affect the lag measurements of \hei\ and \heii. Virial and
infalling gas motions coexist in this campaign, which is different from
previous results, implying the evolutionary kinematics of BLR. Based on our
measurements and previous ones in the literature, we confirm that the BLR of
NGC~4151 is basically virialized. Finally, we compute the black hole mass
through multiple lines, and the measurement from \hb\ to be $
3.94_{-0.72}^{+0.90} \times 10^7 M_{\odot}$, which is consistent with previous
results. The corresponding accretion rate is $0.02_{-0.01}^{+0.01} L_{\rm Edd}
c^{-2}$, implying a sub-Eddington accretor.
