Chinese antitrust authorities required Google Inc. to keep its Android mobile-device software broadly available to manufacturers as part of its approval of the Internet search giant's purchase of Motorola Mobility Holdings Inc., a move that underscores Beijing's increasing sway in global deal making.

The approval pushes the $12.5 billion deal over its last regulatory hurdle and helps better position Google in its competition with Apple Inc. over dominance in the fast-growing world of smartphones and tablet computers. Antitrust...