In Jinping County in Guizhou, five people have died and four are still missing, according to a statement by the county's information office.
Heavy rain pounded the county from last night until early today, with 202 millimeters of precipitation recorded in some areas.
Traffic, power and telecommunications were all affected, and homes were destroyed.
Around 10,000 residents of 24 counties in Guizhou have been displaced, it said.
The homes of 125 families have been destroyed and 300 more have been seriously damaged, state-run Xinhua news agency reported.
Nearly 300 rescuers are searching for the missing around the mountain, which experienced torrential rain on Sunday and Monday.
In Hunan Province, three residents of Xiangtan County have been reported missing after their home was buried by a landslide this morning.