Doctors said the child, now in a deep coma, could die any time or remain on life support for the rest of her life.
Footage taken by surveillance cameras showed 18 passers-by and drivers ignoring the badly injured toddler until a woman scavenger raised the alarm in the incident last Thursday.
The girl, named Wang Yue and also known as Yue Yue, was seen tottering in an alley when a white minivan hit her. One of the front wheels rolled over her body, footage aired by Southern Television Guangdong (TVS) showed.
The driver did not stop the vehicle, but stepped on the accelerator, and Yue Yue was rolled over once again by the back wheels.
After the first hit-and-run accident, which happened at around 5pm, three people walked past the then motionless Yue Yue lying in the middle of the road. Two of them seemed to have noticed her plight, but chose to look the other way.
Shortly afterwards, a truck drove over her, reported Chinese media.
After the second accident, more people either walked by or swerved their vehicles past Yue Yue. Among them was a mother taking her four-year-old girl home from kindergarten.
None of them stopped to help, reported Chinese media.
Nearly seven minutes after the minivan ran over Yue Yue, the rubbish collector spotted her and moved her to the side of the road. She then went to find the parents.
A young woman - later identified as Yue Yue's mother - appeared and carried the child away.
Closed-circuit television footage of the accident obtained by Guangdong media has circulated rapidly online, sparking outrage on China's hugely popular social media sites.
Media commentators and netizens decried the cold-blooded response of the passers-by and the lack of empathy in modern society, reported Xinhua news agency.
One netizen on Sina Weibo, a Chinese micro-blog similar to Twitter, wrote: 'This society is seriously ill. Even cats and dogs should not be treated so heartlessly.'
Another wrote: 'When we denounce these bystanders, we must remind ourselves that they are among us.'
Yue Yue's father, who did not give his full name, said the child had wandered away from the family's metal wares shop when the mother was bringing in the laundry. His wife ran out to look for her, but took a different direction. Yue Yue was found about 50m from their shop.
The mother said the child might have a better chance of survival if someone had come to her aid before she was run over by the truck. 'I am praying for a miracle to happen so that my girl can wake up,' she was quoted as saying by Chinese media.
The couple, both migrant workers from Shandong province, also have a seven-year-old son.
Police said the drivers of both vehicles have been arrested.
