  Overshooting and semiconvection are among the most uncertainties in the
evolution of massive stars. Complete mixing over a certain distance beyond the
convective boundary (Stothers \& Chin 1985) and an exponentially decaying
diffusion outside the convection zone (Herwig 2000) are commonly adopted for
the overshoot mixing. Recently, Li (2012, 2017) developed the $k$-$\omega$
model, which can be used in both convection zones and overshooting regions. We
incorporated it in calculations of $30M_{\odot}$ stellar models. We find that
in the main sequence stage, models with the $k$-$\omega$ model are almost
identical to models with complete mixing in the overshooting region beyond the
convective core, and the overshooting in the $k$-$\omega$ model is equivalent
to an overshooting distance of about $0.15H_P$. In the post main sequence
stage, we find that the overshooting below the bottom of the intermediate
convection zone beyond the hydrogen-burning shell can significantly restrict
the size of the hydrogen-depleted core, and can penetrate effectively into the
hydrogen-burning shell. These two effects are crucial for the evolution of the
core helium burning stage. During the core helium burning stage, we find that
the overshooting model based on the $k$-$\omega$ model results in a similar
complete mixing region but a much wider partial mixing region than the
overshooting model based on Herwig (2000). In particular, the overshooting
distance in the core helium burning stage may be significantly smaller than
that in the main sequence phase for massive stars.
