Li captured her eighth career WTA title and first since Shenzhen last year. Peng is now winless in six finals.
The No. 3-ranked Li is hoping to build momentum heading into the Australian Open, where she has reached the final in two of the past three years. She lost to Victoria Azarenka in last year's final and fell to Kim Clijsters in 2011.
Li retired against Zheng Jie in the only other WTA Tour final featuring two Chinese players, at the Estoril Open in 2006.