Halep, who will take over as number one in the next rankings, broke Garcia's serve in the first game of the match but the 23-year-old hit back immediately, breaking the Romanian twice to win the first set.
With the score tied at 3-3 in the second set, Garcia saved nine consecutive break points in the seventh game, before taking a 4-3 lead but Halep recovered to force a tiebreak.
The Frenchwoman became the first to complete the Wuhan and Beijing double and is now on track to qualify for the season-ending WTA finals, as her win took her past Briton Johanna Konta to number eight in the Race to Singapore rankings.
Halep's record at finals this year is underwhelming, with the 26-year-old winning just one of her five finals so far - the Madrid Open in May.
(Reporting by Aditi Prakash in Bengaluru; Editing by Toby Davis)
