The Blitzboks topped their pool before defeating England 21-14 in the Cup quarter-finals on day two of the Las Vegas Sevens.
The defending champions will now face Fiji in the semi-finals (10:32pm on Sunday, SA time), after the islanders smashed France 31-12.
Neil Powell's side were made to work hard for their victory against England, with tries from Branco du Preez, Seabelo Senatla and Kwagga Smith eventually sealing a come-from-behind win.
South Africa had earlier been held 19-19 by USA in their final pool match, but topped the pool courtesy of a better points difference.
Photo: World Rugby/Martin Seras Lima