  The mean charge sum rule for the light sea quarks in the nucleon which holds
under the same theoretical footing as the modified Gottfried sum rule shows
that a usual parameterization of the strange sea quark distribution
underestimate its contribution in the small $x$ region. We give a discussion of
the soft pion contribution at high energy as a possible explanation of the
saturation of the sum rule and show that it naturally explains why the strange
sea quark is suppressed in the region above $x \sim 0.01$ while it becomes
abundant below it.
