Wang Yun, 39, had unsuccessfully appealed the sentence, initially handed down in September 2020 by the Jiaozuo city intermediate people's court, in Henan province.
On Thursday, the same court verified Wang's identity, escorted her to the execution ground and carried out the death sentence, a court statement said, according to state media.
In March 2019, Wang purchased some sodium nitrite after being involved in a dispute with a fellow teacher.
The next morning at the kindergarten she added some of the chemical compound into the children's "eight treasures porridge", the court ruled, according to state media.
"Eight treasures porridge" is a sweet-flavored rice-based porridge which is very popular in China.
In January 2020, one of the children died of multiple organ failure caused by the poisoning.
Two dozen others suffered minor injuries, state media reported.
Wang's is one of several high profile cases of deaths or violence in Chinese kindergartens in recent years.
A 25-year-old man was suspected of attacking a kindergarten in China's Guangdong province on Monday, killing six people and injuring one, triggering an outpouring of concern about violence against children at school.