  We present the quantum kinetic equation for spin polarization of massive
quarks in leading log order of perturbative QCD, which describes time evolution
of the spin density matrix in momentum space of a massive quark interacting
with a background QCD plasma. We find that the time evolution operator of the
spin density matrix, or the quantum kinetic collision terms, are universally of
order $\alpha_s^2\log(1/\alpha_s)$ in terms of the QCD coupling constant
$\alpha_s=g^2/(4\pi)$. Our quantum kinetic equation is valid for an arbitrary
quark mass $m\gg m_D\sim gT$, where $m_D$ is the Debye mass, and can be used to
study relaxation dynamics of spin polarization of massive quarks in
perturbative QCD regime.
