Officials said five children were taken to hospital in a critical condition after the incident in Jiangsu province.
It follows a knife attack on Wednesday in the south of the country, in which 16 pupils and one teacher were injured.
Earlier that day, a doctor convicted of stabbing eight children to death in Fujian province in March was executed.
The alleged assailant in Jiangsu was named by police as Xu Yuyuan, a 47-year-old unemployed local man.
Reports say he attacked the children at the Zhongzin pre-school in Taixing city as lessons began in the morning, stabbing a security guard who tried to stop him.
Police said Mr Xu, who was detained shortly afterwards, was carrying a 20cm (8in) knife, the state-run Xinhua news agency reported.
"The gate-keeper, teachers, and students were attacked. The injured are receiving treatment in hospital. We don't have any reports of deaths yet
," an official with the Taixing city government told AFP news agency.
An official named Zhu told AFP the critically-injured children were now in a stable condition.
Most of the injured children were reported to be four-year-olds from the same class.