We study the direct product decomposition of quantum many-valued algebras (QMV algebras)which generalizes the decomposition theorem of ortholattices (orthomodular lattices).In detail,for an idempotent element of a given QMV algebra,if it commutes with every element of the QMV algebra,it can induce a direct product decomposition of the QMV algebra.At the same time,we introduce the commutant C(S) of a set S in a QMV algebra,and prove that when S consists of idempotent elements,C(S) is a subalgebra of the QMV algebra.This also generalizes the cases of orthomodular lattices.