The man, surnamed Cai, killed his wife, eight-year-old daughter and seven-year-old son in their home before committing suicide in Wushizhuang Village, Datong County, county public security bureau chief Qi Chunling said.
A police investigation found that the murders happened in the early hours of yesterday, state-run Xinhua news agency reported.
Cai had been in dispute with his wife, as the couple - both working temporary jobs in nearby cities - did not get along well, Qi said.