  In quantum mechanics and quantum information, to establish the orthogonal
bases is a useful means. The existence of unextendible product bases impels us
to study the `entanglement bases' problems. In this paper, the concepts of
entanglement bases and exact-entanglement bases are defined, and a theorem
about exact-entanglement bases is given. We discuss the general structures of
the orthogonal complete bases. Two examples of applications are given. At last,
we discuss the problem of transformation of the general structure forms.
