The Englishman made six birdies to take his total to 15-under 201. England's Ross McGowan was second after also shooting a 66.
Westwood has also opened up a five-shot advantage over Rory McIlroy of Northern Ireland, his only remaining rival for the Race to Dubai. Should he win both titles, Westwood will receive $2.75 million and be Europe's No. 1 player for the first time since 2000.
He believes his confidence will be high going into the fourth round.
"I looked at the names on the leaderboard," he said. "And I have won 30 tournaments in my career and no one else has closed out as many tournaments as I have.
"The Race to Dubai situation is very tense, but I have won it before so I know how to deal with the pressure."
The 27-year-McGowan is certainly inexperienced, playing in only his second full season on the European Tour and only recording his first victory at the Madrid Masters in October.
A run of four birdies from the sixth hole on Dubai's Earth Course took McGowan briefly into the lead until Westwood responded with three birdies from the ninth.
"One of the goals I set myself when I started playing golf was reaching the top of the game," McGowan said. "And it's one step at a time. And I am just out there to win."
The 20-year-old McIlroy had led the European Money List going into the tournament but fell five shots behind after a 69. He is seeking to become the youngest player since Seve Ballesteros to in 1979 to be the No. 1 European player.
The Northern Irishman made six birdies in 15 holes to be one shot adrift of Westwood, but his game then collapsed. Three errors left him in a tie for third place at 10 under with Ireland's Padraig Harrington and Alexander Noren of Sweden.