The suspect, a 23-year-old whose last name is Kong, entered the kindergarten by climbing a wall and then sprayed the victims with sodium hydroxide, according to local authorities in Qayuan City, Yunnan Province.
The attack took place on Monday at 3:35 pm local time, authorities announced on Weibo, a social networking site like Twitter.
About 51 children and three kindergarten teachers were admitted to the hospital, two of them with "serious symptoms".
Police arrested Kong almost an hour after the attack.
"Because his parents divorced when he was a child, the lack of family warmth resulted in him developing a mental disorder," said local authorities, adding that he had problems with both his personal life and work.
All this caused him "a pessimistic mentality and thoughts of revenge against society," they noted.
Violent attacks on students are common in China, where fatalities have occurred in recent years, usually with perpetrators using knives.
Last April, a 28-year-old man killed nine elementary school students as they marched on one of the deadliest knife attacks in the country in recent years.
The perpetrator, who stated that he had been bullied as a student in the northern Chinese province of Shanxi, was executed in September last year.
Later in 2018, a woman armed with a knife injured 14 children in a kindergarten in Sichuan Province.
The 39-year-old perpetrator injured the students as they were returning to their classes after their morning exercise.