  The pion electromagnetic form factor with leading and next-to-leading twist
corrections are studied in the framework of pQCD approach. We find that, at
small momentum transfer regions, Sudakov effects cannot provide a strong enough
suppression of the non-perturbative contributions coming from large transverse
separations, but at large momentum transfer region, non-perturbative
contributions can be effectively suppressed. So pQCD approach can be applied at
large momentum transfer region. At the energy region where experiment can
access so far, i.e. Q < 4GeV, pQCD prediction can not be precise because there
may be a quite large part of contributions coming from non-perturbative region.
The calculation of power corrections may not be performed systematically in
pQCD framework.
