  In this paper we propose that, quantized and nearly half-quantized intrinsic
anomalous Hall effect can be induced by in-plane external magnetic field
through the Zeeman coupling in non-magnetic 2D systems with sizeable
spin-orbital coupling but without two-fold rotational symmetry. An analytical
result is derived for 2D electron gas model with $C_{3v}$ symmetry. Based on
the $\boldsymbol{k\cdot p}$ Hamiltonian derived from first principle
calculations, we find that quantized and nearly half-quantized conductance can
be observed in $\mathrm{Sb_2Te_3}$ thin film in the clean limit with strong
in-plane magnetic field $B>20\ \mathrm{T}$ and low temperature $T<100\
\mathrm{mK}$.
