  There is much debate about the channels for astrophysical origins of the
stellar-mass binary black hole (BBH) mergers detected by LIGO and Virgo. Active
galactic nuclei (AGNs) are promising sites for the efficient formation and
rapid mergers of BBHs due to migration traps in high-density gas disks within
an inner radii. In this paper, we carry out Monte Carlo simulations to explore
the mass properties of mergers over time and hierarchical mergers -- with one
of the black holes (BHs) being the remnant of a previous merger. We find that
the predicted merger rate is $\sim 27-37~{\rm Gpc^{-3}~yr^{-1}}$ and the
detection rate of LIGO/Virgo accompanying with extreme mass-ratio mergers will
increase in the late stage of AGNs. The fraction of hierarchical mergers is
$\sim 24\%$, and its mass-ratio peak is $\sim 0.15-0.35$. Compared with the
low-generation mergers in hierarchical mergers, the mass ratio of
high-generation mergers has a flatter distribution around its peak. These
reveal that the BBH mergers detected by LIGO/Virgo with the extreme mass ratio
or heavy component masses can be well explained in AGN channel.
