The toddler was hit by a van on Thursday in the city of Foshan.
After the van sped off, several pedestrians and vehicles passed the girl without stopping. Several minutes later she was hit by another vehicle.
A rubbish collector finally helped her, but she is said to be seriously hurt.
The incident was captured on surveillance cameras and aired on local media.
The footage showed the van hitting the little girl, pausing briefly while she was under the vehicle and then driving off, running over her legs.
It then showed about a dozen passers-by, including cyclists, a motorcyclist and a woman and child, noticing the little girl lying injured in the street but walking on.
There’s been so many cases where people have been treated unjustly after doing good things”
After she was hit by the second vehicle, a rubbish collector spotted the little girl and moved her to the kerb, then began looking for her mother.
The child, Yue Yue, was taken to hospital for emergency surgery but pronounced brain dead on Sunday, the China Daily reported.
The newspaper said she had wandered off while her mother went to collect some laundry.
The drivers of both vehicles have now been arrested, the newspaper said, but the incident has also triggered outcry among Chinese citizens.
It provoked a storm of comment on microblogging site Weibo.
“Even pigs and dogs are better than they are!” said one angry contributor about the passers-by.
“In China, there’s no bottom line for human ethics anymore! China is ‘smashing’ new records again and again!” commented another.
Others were more reflective. “Now people ignore everything other than money. This society is lacking people with a conscience badly.”
Some said they understood the dilemma for the passers-by – that if they helped out they might incur costs or be blamed for the accident.
The China Daily reported incidents in January in which elderly men who fell in the street were left alone because people did not want to get involved.
It cited an earlier case in which a man, Peng Yu, who helped an injured elderly lady to hospital was then found by a court to be liable for some of her medical costs.
Another case – in which an elderly woman believed to have fallen in the road accused a man, Xu Yunhe, who stopped to help her, of hitting her with his car – also attracted considerable attention.
“There’s been so many cases where people have been treated unjustly after doing good things,” one comment said.
“I am not as rich as Xu Yunhe and Peng Yu are, we are all poor grassroots people,” said another. “If we get caught in a scam, this is it. All we can do is to dial 120 (the emergency number).