The incident occurred in a darkened stairwell at a primary school in Tongjiang county in the southwestern province of Sichuan, the state-run Xinhua news agency reported.
Five of the injured children were reportedly in critical condition in a local hospital.
Local newspaper reports cited by the Sina.com website said the panic was caused when a child shouted that he had seen a ghost.
Other children joined in the cries, sparking a mass panic and causing several to trip down the staircase.
Xinhua said the cause of the accident was under investigation.
The pupils were leaving evening classes on Tuesday night when the stampede occurred.