Twelve months ago the British teenager announced her arrival on the world stage with back-to-back wins over Kim Clijsters and Li to reach the fourth round of a grand slam for the first time.
But sixth seed Li was in very good form on Friday and, although Robson upped her level in second set, it was not enough as the Chinese player won 6-2 7-5.
The pair opened the schedule on Arthur Ashe, which meant they began the match in front of virtually empty stands.
Robson enjoys the big stage but she began poorly, dropping serve in the opening game, and was thoroughly outplayed in the first set.
The 19-year-old was spraying her forehand to all parts and could make no impression with her serve.
She battled hard to hold on to her serve to trail only 1-2 but Li broke again to take a stranglehold on the set.
The 31-year-old, who was eager to take revenge for last year, is one of the cleanest strikers of the ball on tour and she was drilling her returns back at Robson's feet.
The 30th seed is very popular here after her run last year and the few fans there were in the stands tried to spur her on as she held serve to make it 2-5.
Li had no trouble clinching the set but Robson began the second set playing much better and raced into a 3-0 lead - with a little help from her opponent, who hit two double faults in one game.
Robson had 0-30 in the next game but Li generally served very well, hitting 11 aces in the match, and she did not give her opponent much chance to sniff a double break.
That proved a crucial hold as Robson dropped serve again in the next game, saving two break points but not a third.
The British number one was playing much better than in the first set but was still below her best - a tally of 30 unforced errors and seven winners will make painful reading.
Much of that was to do with Li, who is a superb mover and was able to cope with the power of Robson.
The teenager matched Li well until the 11th game, when another return arrowed back at Robson's feet forced the error and gave Li the chance to serve for the match.
Robson threw everything at her opponent but it was to no avail, Li clinching victory on her second match point with a second-serve ace.
Robson's ranking will drop a little from her current position of 32 but it has nevertheless been a promising week for the teenager, especially considering she is still affected by a wrist injury that meant she came into the tournament having played only two matches since Wimbledon.