  We investigate the feasibility of the Si I infrared (IR) lines as Si
abundance indicators for giant stars. We find that Si abundances obtained from
the Si I IR lines based on the local thermodynamic equilibrium (LTE) analysis
show large line-to-line scatter (mean value of 0.13dex), and are higher than
those from the optical lines. However, when the non-LTE effects are taken into
account, the line-to-line scatter reduces significantly (mean value of
0.06dex), and the Si abundances are consistent with those from the optical
lines. The typical average non-LTE correction of [Si/Fe] for our sample stars
is about $-$0.35dex. Our results demonstrate that the Si I IR lines could be
reliable abundance indicators provided that the non-LTE effects are properly
taken into account.
