  In this paper, we study a sextic del Pezzo fibration over a curve
comprehensively. We obtain certain formulae of several basic invariants of such
a fibration. We also establish the embedding theorem of such a fibration which
asserts that every such a fibration is a relative linear section of a Mori
fiber space with the general fiber $(\mathbb{P}^{1})^{3}$ and that with the
general fiber $(\mathbb{P}^{2})^{2}$. As an application of this embedding
theorem, we classify singular fibers of such a fibrations and answer a question
of T. Fujita about existence of non-normal fibers.
