Li was rarely troubled in the one-sided match, outclassing her opponent in 67 minutes to reach the final four after last year’s final loss to Victoria Azarenka, Xinhua reported.
Li broke Pannetta in the first game of the match, following up with two more breaks to lead the first set 5-0. The Italian, who stunned No.9 seed Angelique Kerber in the fourth round, broke back in the sixth game but Li still managed to take the set 6-2.
Li Na took 32 minutes to win the second set 6-2 by breaking Pennetta twice.
Li and Pennetta were tied 2-2 in their previous four meetings. Pennetta defeated Li 6-2, 7-6 (7-4) in their last meeting in Sydney in 2010.
The Italian has played the best tennis of her career since returning last year from a wrist injury, which caused her ranking to drop as low as No.166.
Back to the court from injury, Pennetta reached her first Grand Slam semifinal at the US Open and then her first quarterfinals at the Australian Open.
Li will play her fourth semifinal in five years at the Melbourne Park. She will play against the winner between No.14 seed Ana Ivanovic of Serbia and 30th-seeded Canadian teenager Eugenie Bouchard.