  In this paper, we first design a type of Bang-Bang (BB) operation group to
reduce the phase decoherence in a {\Xi}-type n-level quantum system based on
the dynamical decoupling mechanism. Then, we derive two kinds of dynamical
decoupling schemes: periodic dynamical decoupling (PDD) and Uhrig dynamical
decoupling (UDD). We select the non-diagonal element of density matrix as a
reference index, and investigate the behavior of quantum coherence of the
{\Xi}-type n-level atom under these two dynamical decoupling schemes proposed.
At last, we choose a {\Xi}-type six-level atom as a system controlled, and use
the decoupling schemes proposed to suppress the phase decoherence. The
simulation experiments and the comparison results are given.
