The　structural　optimization　and　vibrational　frequency　analysis　have　been　carried　out　for　eleven　designed　Se-4　isomers　with　Hartree-Fock,　density　functional　theory　and　MP2　methods,　indicating　the　five　isomers　are　stationary　points　on　the　potential　energy　surface　of　Se-4　molecules.　The　geometry　structure　analysis　demonstrates　that　the　electronical　correlation　obviously　affects　the　optimization　results　of　bond　lengths,　but　both　HF　exchange　and　electronical　correlation　play　important　roles　in　the　optimization　of　bond　angles.　The　Frontier　Molecular　Orbital　(FMO),　Mulliken　population　and　dipole　moments　of　Se-4　molecules　have　also　been　investigated.　The　analysis　results　of　FMO　show　that　Se-4　molecules　prefer　negative　ion　to　positive　one.　With　wide　LUMO-HOMO　energy　gaps,　Se-4　molecular　clusters　have　certain　chemistry　stability.　It　can　be　concluded　from　Mulliken　population　analysis　that　Se-4　Molecular　clusters　show　obvious　trend　of　forming　negative　and　positive　ion　couples.　It　has　been　anticipated　from　the　dipole　moments　analysis　that　Se-4　may　have　low　solubility　in　strong　polar　solvent　like　water　but　can　dissolve　in　weak　polar　solvent.