He trimmed eight shots off the par-72 course and did not drop a shot for the second day running.
Westwood picked up four birdies coming in and four more going out, leaving him in a commanding position on 20 under par - with Charl Schwartzel and Michael Thompson posing the nearest thing to a threat on nine under.
American John Daly, who had been Westwood's nearest challenger at the end of the first day, shot a one-over 73.
Plain sailing: Westwood takes the boat to the 17th green
England's Simon Dyson moved to five under, a shot behind Daly, with a 70.
Westwood wrote on Twitter: 'Arguably a better round than first day in windy conditions! 64 to add to a 60. For sure the best I've ever played.'
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