We study the topological feature in the QCD vacuum based on the hypothesis of abelian dominance. The topological charge QSU(2) can be explicitly represented in terms of the monopole current in the abelian dominated system. To appreciate its justification, we directly measure the corresponding topological charge QMono, which is reconstructed only from the monopole current and the abelian component of gauge fields, by using the Monte Carlo simulation on SU(2) lattice. We find that there exists a one-to-one correspondence between QSU(2) and QMono in the maximally abelian gauge. Furthermore, QMono is classified by approximately discrete values.