  The particular giant X-ray bump of GRB 121027A triggered by \emph{Swift} is
quite different from the typical X-ray flares in gamma-ray bursts. There
exhibit four parts of the observed structural variabilities in the rise and
decay phase of the bump. Considering the quality of four parts of the data, we
can only analyze the data from about 5300 s to about 6100 s in the bump using
the stepwise filter correlation method (Gao et al. 2012), and find that the
$86^{+5.9}_{-9.4}~\rm s$ periodic oscillation may exist, which is confirmed by
the Lomb-Scargle method (Scargle 1982). Furthermore, a jet precession model
(Liu et al. 2010) is proposed to account for such a variability.
