The police's public statement said the attack at the Xinshiji Kindergarten in the city's outskirts took place at 9.30 in the morning as the children were returning to classes. She was later restrained by the school's security guards and staff members, who handed over the assailant to the police.
She has since been arrested. The videos showed small children bleeding from severe cuts to their faces at the entrance to the kindergarten as stunned adults looked on.
According to BJNews, four of them are seriously injured and they have been transferred to the Children's Hospital of Chongqing Medical University.
However, China knife attack is not new as in last few years a series of knife and axe attacks are observed.
Such assaults have been blamed largely on the mentally ill or people bearing grudges.
The police were investigating the incident but did not disclose if it had discovered her motive.
Large crowds gathered at the scene following the incident, and that the attack had shocked residents of the city, a metropolis of some 30 million people, the report said.
Knives are most commonly used because gun controls are extremely strict in China.
A vehicle crashed into a large crowd of people in Hengdong County, central China's Hunan Province on Wednesday evening, killing 11 and injuring a further 44.
Chinese law restricts the sale and possession of firearms, and mass attacks are generally carried out with knives or homemade explosives.
Nearly 20 children were killed in school attacks in 2010, prompting a response from top government officials and leading many schools to add gates and security guards.
In January 2017, a man armed with a kitchen knife stabbed and wounded 11 children at a kindergarten in southern Guangxi Zhuang autonomous region.