AB, Behardien help Proteas to 341
He fell agonisingly short of a century as South Africa set a 342-run target.
De Villiers made 99 runs off 82 balls to help his teammates to 341 for six after they were put into bat first.
Farhaan Behardien also contributed a smashing 64 runs from 31 balls.
UAE are still searching for their first win in the event.
Victory for South Africans will see them move up second place in Pool B.
Batsman David Miller who made 49 runs is optimistic about the match.
"The guys are in a great space. I think all the top six or seven batters have made a contribution throughout the competition and that's what we really need going into the quarter finals,'' he said.
UAE captain Mohammad Tauqir surprisingly opted to bowl first on a pitch that appeared perfect for batting, with the decision paying early dividends when Hashim Amla miscued a pull shot to depart on 12.
Quinton de Kock and Rilee Rossouw made the most of some wayward bowling in a 68-run partnership, with Rossouw the aggressor as the out-of form de Kock tried to play himself in.
But the youngster's woes continued when he nicked an edge to the keeper on 26, leaving him with an average of under eight from his six innings at the tournament.
Rossouw (43) followed three overs later, deceived by a slower ball from Tauqir that he scooped straight back to the bowler.
South Africa were looking unexpectedly shaky at 96 for three and it could have been worse, with the UAE fumbling a chance to run out Miller on seven and Fahad Al Hashmi having a good shout for lbw against de Villiers turned down.
They made the most of their reprieves to bring up 100 off 99 balls, with the Proteas skipper notching his 45th one-day international half century.
Miller fell just short of his own half century, clean bowled by Mohammad Naveed on 49 attempting a pull shot.
De Villiers was dropped on 65, with the close shave adding urgency to his innings as he unleashed a flurry of powerful shots, including sixes from consecutive deliveries off Amjad Javed.
Javed had his revenge when he caught de Villiers one run shy of a century, although Behardien proved just as destructive.
He plundered 24 runs off Javed's final over to help set a total that will be difficult for the UAE to reach.
(File photo: Gallo Images)