La2/3Sr1/3MnO3　films　with　highly　(110)　preferred　orientation　were　deposited　on　Si　(100)　substrate　without　any　buffer　layer　by　using　a　pulsed　laser　deposition　technique.　The　effects　of　oxygen　pressure　on　crystallinity,　preferred　orientation,　surface　morphology,　magnetic　and　electrical　transport　properties　of　the　films　were　investigated.　The　results　show　that,　comparing　to　the　films　deposited　at　other　ambient　oxygen　pressure,　La2/3Sr1/3MnO3　films　deposited　at　10　Pa　presented　highly　(110)　preferred　orientation　with　highly　crystalline　quality　and　have　more　homogeneous　grain　size　distribution　as　well　as　dense　microstructure.　Meanwhile,　the　roughness　of　the　films　also　shows　the　smallest　root　mean　square　value　(Rrms)　of　1.35　nm.　The　film　with　the　(110)　preferred　orientation　shows　higher　saturated　magnetization　(Ms),　higher　metal-insulator　transition　temperature　(TM-I)　and　lower　resistivity　(ρ)　than　that　without　preferred　orientation　one.