The victory was also the Dane's second in Beijing, eight years after the first.
The unseeded Sevastova downed U.S. Open champion Naomi Osaka in the semifinal, but couldn't handle the second-seeded Wozniacki's punishing groundstrokes.
Though Sevastova threatened late in the second set, Wozniacki broke her in the ninth game to wrap up the title, the 30th of her career.
Wozniacki said eight was her lucky number and, having won in Beijing eight years ago, she "felt it was my year."
In the men's final, Juan Martin del Potro faced Nikoloz Basilashvili of Georgia.
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