The Dane is now virtually assured of a semi-finals berth after losing just four games in two matches, while Halep lives to fight another day after her opening straight sets victory over Caroline Garcia gives her a 1-1 record in the Red Group.
It's her first at the WTA Finals and keeps alive her dream of winning the end-of-season tournament.
Unlike Svitolina who seems to struggle on a slow surface, Garcia can easily adapt her game to it.
"It's a great match for me to play and it's another player who is moving well on court, giving few free points".
Woznaicki, 27, produced a near ideal display to dismantle Halep 6-0, 6-2 at the WTA Finals to record her second dominant win of the tournament following her opening win over Elina Svitolina.
If Wozniacki sailed through her match, there was nothing straightforward about Garcia's win over Svitolina in yesterday's later clash. I mean, I wish I knew what was happening today with my game, because even though it's 7-5 in the third - my game was completely off.
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The world No 8, known for her powerful baseline hitting, began the match in a positive fashion bringing up two break points in Halep's opening service game of the match.
Aged 23, Elina Svitolina (4 WTA) has put together a solid display of tennis throughout the most of 2017. "I'm thinking about playing better than today, definitely", the 26-year-old said.
"There were so many ups-and-downs in this match, a little bit like the one we played in Beijing (where Garcia also won in three sets)". "I'll try to forget this day and try to play my next game as if nothing had happened", said the Ukrainian, dépitée. "Also I did some good shots, good points, and I missed too many to win a match".
Halep will hope to advance with a win over Svitolina on Friday, while Garcia faces the unenviable task of taking on Wozniacki with the world number eight needing a victory to stand any chance of reaching the last four. "It was a battle on every single point, and I'm just happy to be through".
Another forehand error handed Wozniacki a match point after a little more than an hour, which she duly converted with a forehand victor. I was happy with... "It was very hard, a lot of emotion, some up and down, but at the end I could control myself better than she did".