Williams, who clinched the Brisbane International last month, beat Serbia's Jelena Jankovic 6-2 6-2 to move into the last four of the competition.
The world number one is yet to drop a set in the competition after beating fifth seed Jankovic for a fifth time in a row at the WTA Premier hard-court event.
Eighth seed Caroline Wozniacki needed just over an hour to see off Romania's Sorana Cirstea 6-1 6-2.
The world number 11 was rarely troubled by Cirstea, winning 79 per cent of points on her first service to book a semi-final clash with fellow former world number one Venus Williams.
The American world number 44 was too strong for Italian Flavia Pennetta, winning through 6-3 7-5.
Qualifier Pennetta beat number two seed and former champion Agnieszka Radwanska in the previous round, but saved just three of nine break points against her opponent before bowing out.
The American wildcard has never lost to Wozniacki in five attempts and will be hopeful of recording a sixth straight win and moving into her second final of 2014.
Alize Cornet completed the semi-final line-up when she saw off Spain's Carla Suarez Navarro 7-5 6-3.
France's world number 26 secured a semi-final clash with Serena Williams, despite double faulting five times and failing to save any of three break points.