Miyazato, who led by a single shot after, ended the day at 11-under 133, three strokes ahead of Song-Hee Kim (64) and Na Yeon Choi (67), who are knotted at 8-under 136.
Miyazato is seeking her fifth tourney win of the season. A win would move her back into the world No. 1 ranking.
It was a rough day for Juli Inkster, who despite shooting a 5-under 67 was disqualified for using a weighted device on her club when she was taking practice swings on the 10th tee.
Jiyai Shin (68) and Cristie Kerr (67) were tied one stroke further back at minus-7.
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