Facing windy conditions once again at Ko Olina, Miyazato shot a 2-under 70 to go into the final round with a 10-under 206 total.
"But it's still tough to play out there," Miyazato said. "I said to myself to just stay focused.
"It was a really strong finish. I was really happy. The 18th is a really difficult tee shot, and of course the second shot was really tough, too. I had a really nice number today. I just hit a nice and easy 7-iron, and just a short bounce in front of the green. It was perfect, so I'm very happy with that."
Miyazato admitted that a three-shot lead would count for little if the strong winds keep up.
"Just need to focus on my game one for day," Miyazato said. "Keep my swing tempo and try to hit the fairways and greens and make some putts. So that's the key points."
Spain's Azahara Munoz, who held a share of the overnight lead with Miyazato, finished the day in second along with Cristie Kerr.
Munoz had a 73 while Kerr shot a 71.
"I think I played pretty solid," Kerr said. "I had some putts on the front that I misread. I thought it played a little tougher today where the pins were and the way the wind was a little different angle and a little stronger."
World number one Yani Tseng was 6-under with So Yeon Ryu, Jiyai Shin, Meena Lee and Angela Stanford ahead of Saturday's final round.
"I played a really solid round today," Tseng said. "I made a lot of putts. I'm still thinking to win. Four or five shots is really nothing on this golf course. It was really windy. You just go out there and have another fun day and enjoy."