Dimuth Karunaratne and Kaushal Silva safely guided their side to 84 without loss in their second innings.
AB de Villiers will captain SA in the opening game at the WACA on Friday.
South Africa beat New Zealand by 72 runs and took a 2-0 lead in the ODI series.
South Africa are among the favourites to win thequadrennial tournament.
New Zealand's Kane Williamson has been banned from bowling due to an illegal arm action.
The disgraced Kiwi cricketer says greed and frustration motivated his actions.