The　main　characteristics　of　molecular　crystals　RbC8H5O4,　TlC8H5O4　and　KC8H5O4　is　that　the　structural　units,　which　are　located　on　crystal　lattices,　essentially　keep　the　shape　and　feature　which　they　have　in　the　free　state.　Using　laser　Raman　spectroscopy,　a　structural　analysis　is　made　to　classify　the　internal　vibration　modes　of　rubidium　acid　phthalate,　RbC8H5O4,　and　to　perform　a　symmetrization　analysis　of　each　fundamental　direct　product　representation.