Aiming　at　two　different　installation　modes　of　a　nut　when　the　corresponding　ball　screw　was　fixed　at　one　end　and　supported　at　the　another,　a　comparative　study　on　their　influences　on　the　load　distribution　of　the　ball　screw　was　performed.　The　different　load　states　of　the　screw　for　the　two　nut　installation　modes　were　firstly　analyzed　qualitatively.　Then,　a　ball　screw　load　distribution　model　considering　varying　of　actual　contact　angle　was　established.　Using　the　model,　the　influence　laws　of　the　nut　installation　modes　on　the　normal　load　and　actual　contact　angle　of　each　steel　ball　were　quantitatively　investigated.　The　numerical　results　showed　that　the　distributions　of　the　normal　load　and　contact　angle　are　more　even　when　the　connecting　flange　of　the　nut　is　installed　far　from　the　screw＇s　fixed　end;　in　addition,　the　nut　installation　mode　has　no　significant　effect　on　the　axial　stiffness　of　the　ball　screw.　The　study　results　provided　a　theoretical　basis　for　reasonable　installation　or　maintenance　of　ball　screws,　they　were　significant　for　enhancing　performances　of　ball　screws　and　prolonging　their　life.