  We discuss the QCD effects of the higher-twist operators in the nucleon
spin-dependent structure functions measured by the polarized deep inelastic
leptoproduction.
  We particularly study the renormalization of the twist-3 and twist-4
operators within the framework of operator product expansions and
renormalization group methods in perturbative QCD.
  Emphasis will be placed on the role of the operators proportional to equation
of motion which appear in the mixing of the higher-twist operators through
renormalization.
  The logarithmic and power corrections in $Q^2$ due to the lowest spin
higher-twist operators are discussed for the first moment of $g_1$ structure
function, Bjorken and Ellis-Jaffe sum rules, as well as the lower moments of
$g_2$ structure function.
