  The only experimental information on the parton distribution of kaons was
obtained from the scarce kaon-induced Drell-Yan cross section data. From these
data, evidence for a valence $u$ quark distribution of kaon softer than that of
pion was found. We study the feasibility to extract kaon's valence quark
distribution via the existing kaon-induced J/psi production data. We compare
the NA3 data on the K- / pi- and K+ / pi+ ratios for J/psi production on a
platinum target with theoretical calculations based on the color-evaporation
model. We show that the NA3 data on J/psi production provide an independent
evidence for a valence $u$ quark distribution softer in kaon than in pion. The
data also suggest different gluon distributions for kaon and pion.
