Yuan needed two hours and 13 minutes and seven championship points to subdue Wang, who rallied from 5-2 down in the second set to force a tie-break in the showdown at Austin, Texas.
In her only prior WTA final, Yuan had lost to American Jessica Pegula last October at Seoul.
The matchup was the first all-Chinese WTA final since Wang Qiang defeated Zheng Saisai to take the 2018 Nanchang crown. It was the first all-Chinese final outside Asia since Zheng Jie defeated Li Na in the 2006 Estoril championship match.
World number 68 Yuan rallied from 2-0 down to take the first set, denying 64th-ranked Wang on five of six break chances and converting both of her own, claiming the set on a forehand winner.
After Wang fought back from the brink to force a second-set tie-break, Yuan jumped ahead 6-1 in the decider, only for Wang to save three match points before Yuan claimed the triumph.
Wang was denied her second career WTA title, having won last September's Guangzhou Open in her only other tour final.
