The 24-year-old finished with a hat-trick of birdies to complete an impressive win, having moved into a share of the overnight lead with Stacy Lewis.
Lewis finished in a share of second with Karrie Webb.
The win was Park's second on the LPGA Tour, and the first since the US Open in 2008.
"It feels great. It was four years ago but it feels longer than that," Park said. "I finished the round with some really strong putting today."
"After yesterday, a lot of players were in contention so I knew I had to shoot a good score out there. The greens were a lot quicker than the last five years. I like the fast greens, so I think that really suited me as well."
- Stacy Lewis