Zhang Xingyan, 33, was taken into custody two days after a boy and two girls aged 8 to 9 went missing on their way to school early this week, the city government of Yueyang in southern China's Hunan province said in a statement.
Zhang told police that he coaxed the children into a car less than a kilometer (0.6 miles) from their homes, drove them to another city and killed them in the woods. The children came from two families and knew Zhang, who is from the same village.
Authorities said they found the children's bodies.
A man had demanded a ransom of 900,000 yuan ($150,000) for the children's freedom, but it is unclear if Zhang made that phone call.