  Next-to-leading order approximation of the quark helicity distributions are
used in the frame work of polarized valon model. The flavor-asymmetry in the
light-quark sea of the nucleon can be obtained from the contributions of
unbroken sea quark distributions. We employ the polarized valon model and
extract the flavor-broken light sea distributions which are modeled with the
help of a Pauli-blocking ansatz. Using this ansatz, we can obtain broken
polarized valon distributions. From there and by employing convolution
integral, broken sea quark distributions are obtainable in this frame work. 0ur
results for $\delta u$, $\delta d$, $\delta \bar u$, $\delta \bar d$ and
$\delta \bar s$ are in good agreement with recent experimental data for
polarized parton distribution from HERMES experimental group and also with GRSV
model. Some information on orbital angular momentum as a main ingredient of
total nucleon spin are given. The $Q^2$ evolution of this quantity, using the
polarized valon model is investigated.
