The 30-year-old, who is yet to feature in the Cherries first-team squad this season, will be available when Oxford face Cheltenham this weekend.
He has been snapped up as competition and cover for Ryan Clarke following injuries to Max Crocombe (shoulder) and Wayne Brown (foot).
"He is six foot two, has won promotion from this division with Bournemouth and is a very good goalkeeper," manager Chris Wilder told the club's official website.
"He is someone we have seen a lot over the years and we think he will do an excellent job for us.
"It is unfortunate for Max because we think very highly of him but Max knows that we need someone pushing Ryan while he is unavailable and Shwan fits the bill perfectly."