  Partonic structure of constituent quark (or{\it{valon}}) in the
Next-to-Leading Order is used to calculate pion structure function. This is a
further demonstration of the finding that the constituent quark structure is
universal, and once it is calculated, the Structure of any hadron can be
predicted thereafter, using a convolution method, without introducing any new
free parameter. The results are compared with the pion structure function from
ZEUS Coll. Leading Neutron Production in $e^{+}p$ collisions at HERA. We found
good agreement with the experiment. A resolution for the issue of normalization
of the experimental data is suggested. In addition, the proportionality of
$F_{2}^{\pi}$ and $F_{2}^{p}$, which have caused confusion in the normalization
of ZEUS data is discussed and resolved.
