  The physical properties of striped Hall state in the presence of an external
unidirectional periodic potential is investigated. The study of searching the
optimal orientation of the state is reported for the state at filling factor
$\nu=2+1/2$ and for the state at higher Landau levels at $l+1/2$ where
$l=3,4,5,6,7,8$. It is predicted that two phases of the orientation, parallel
phase and perpendicular phase, exist and a phase transition from one to another
phase occurs.
