Ryu surged into the lead after making seven birdies and an eagle to shoot a 65 on Mission Hills' Blackstone Course and move to 9-under 210 overall.
But the second-ranked Park birdied No. 15 and 17 to move back in front, finishing at 10-under 209.
Norway's Suzann Pettersen (67) and China's Lin Xiyu (73) were two strokes behind Ryu in joint third.
Park is trying to win her second title in as many weeks after capturing the HSBC Women's Champions trophy last week in Singapore.