  Valence quark distributions of pion at very low resolution scale $Q^{2}_0
\sim 0.1~GeV^2$ are deduced from a maximum entropy method, under the assumption
that pion consists of only a valence quark and a valence anti-quark at such a
low scale. Taking the obtained initial quark distributions as the
nonperturbative input in the modified
Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (with the GLR-MQ-ZRS corrections)
evolution, the generated valence quark distribution functions at high $Q^2$ are
consistent with the measured ones from a Drell-Yan experiment. The maximum
entropy method is also applied to estimate the valence quark distributions at
relatively higher $Q^2$ = 0.26 GeV$^{2}$. At this higher scale, other
components (sea quarks and gluons) should be considered in order to match the
experimental data. The first three moments of pion quark distributions at high
$Q^2$ are calculated and compared with the other theoretical predictions.
