Nine deaths were reported in Xishui County of Guizhou Province, which was battered by torrential rain on Sunday and yesterday, state-run Xinhua news agency reported. So far 3,120 people had been evacuated for safety reasons.
Twenty-five homes were washed away and 42 others were seriously damaged.
Economic losses in Xishui County were estimated at 190 million yuan ( USD 30.88 million).
Nine people in Xishui were reported missing in floods and rescue work continued till late last night.
Downpours also battered parts of the southwestern Chongqing Municipality starting Saturday.
Two road workers in Nanchuan District were reported missing, 32 homes collapsed, and 360 people were re-settled. Sanquan, in Nanchuan District, has received 305 mm of precipitation in the past three days, the heaviest downpour since records began, the weather bureau said.
Meanwhile, the whether bureau has warned that strong rains will sweep the quake-hit zone in Yunnan Province, raising the risk of more flooding and landslides.
A 6.5-magnitude quake jolted the southwestern province on August 3, leaving at least 617 people dead.
Rescuers are racing to drain a barrier lake which has raised fears of flooding.
The National Meteorological Centre (NMC) has warned that persistent rain may push up water levels in the lake and urged local authorities to be on alert.
Besides the quake-hit region, most parts of southwestern China will be hit by rain, including Sichuan, Chongqing, Hubei and Guizhou