The children, all from the same kindergarten in Wuwei city, Gansu province, suffered fever, vomiting and stomach ache after having porridge and buns for breakfast at school on Wednesday, Xinhua news agency reported.
Preliminary investigations suggested the food poisoning was as a result of the children eating pork infected with diarrhoea-inducing bacteria, Xinhua said.
Authorities continued to investigate the cause of the incident and the children were being treated and gradually allowed to leave four different hospitals, it said.
As of mid-afternoon Saturday, most of the children had been allowed to return home, according to Xinhua.
Mass food poisonings are frequent events in China, often triggered by the unsafe handling of food.
China has been plagued by a spate of food safety scandals in recent months at home and abroad.