The number one seed was given few scares as she saw off world number 42 Peng 6-4 7-5 to clinch the WTA International hard court event in China - her eighth Tour title.
In what was just the second ever all-Chinese WTA Final, the contest began in a very even manner with both players dropping serve within the opening four games.
Interestingly, the first all-Chinese final also involved Li, as she was forced to withdraw against Zheng Jie in the Portugal Open showpiece eight years ago due to heat illness, but even after Peng moved 4-3 ahead, Li showed resilience as she reeled off the next five games to take the first set and a 2-0 lead in the second.
At 4-1 up, it seemed as though the world number three would see out the game without any dramas, but Peng, eager to halt her winless record in WTA finals, fought back to lead at 5-4.
Not to be denied, Li took the next three games, Peng wasting two break points in the 12th, as the defending champion tasted success at the competition for a second year running.
It leaves Peng without a win in six WTA finals while Li goes into the Australian Open with a head of steam.
She has reached the final of the grand-slam competition twice in the last three years.