Li made short work of the British number one in the first set, winning it 6-2, before a more evenly-contested second set saw Li edge it 7-5 to take the match in straight sets.
The result came a year after Robson had beaten the same opponent at the same stage of the US Open to reach the fourth round of a Grand Slam for the first time in her career, but she admitted that Li outplayed her this time around.
"I thought she played really well. She didn't give me too many chances in the rally, so I never felt I got a rhythm going with my groundstrokes," Robson told PA.
"She was returning really deep. There wasn't a lot I could do in some points.
"It was quite windy when we started the match, so on one side you would have to play more spin and, I wasn't quite doing that very well."