Children at the private Litian Kindergarten in northwest Gansu Province were given the prescription drug ribavirin.
The feeding of drugs without permission of the parents and prescription raised concerns among parents who demonstrated calling for action.
Nie Aiqin, the kindergarten principal, admitted that 50 boxes of ribavirin had been bought since October 2013. Children were given the antiviral drug on two occasions.
On each occasion they were given tablets three times a day to allegedly prevent infectious disease.
More than 280 children who attend the kindergarten have received a health examination. Results are due soon.
Similar cases have been reported this month in the northwestern city of Xi'an, the northeastern city of Jilin and central China's Yichang City.