Heavy rain has left 128 people dead and 42 others missing in five days, figures from the Ministry of Civil Affairs showed on Tuesday.
Rain since June 30 has led to the collapse of 41,000 houses and forced the evacuation of more than 1.34 million people, mostly along the Yangtze River and its tributaries.
Nearly 600,000 people are in urgent need of basic living assistance, with 23.3 million threatened by floods.
The rain has destroyed 295,200 hectares of crops.
Floods and landslides are also affecting telecommunication and electricity facilities, halting or delaying traffic in some regions.
The ministry estimated total economic losses of 38.2 billion yuan (5.7 billion U.S. dollars).
The ministry and the National Commission for Disaster Relief started a level-four emergency response in Hunan and Guizhou on Tuesday afternoon and sent teams to help relief work.
Guizhou has been one of the worst-hit provinces, with 44 dead and 20 missing in floods and landslides.
In Hunan 11 people have died.
Hunan upgraded its emergency response to level-two, sending 30 million yuan in cash, food, clothing, tents and quilts to disaster-hit areas.
In Hubei, heavy rain has left 45 people dead and 11 missing, local civil affairs department said. Direct economic losses are estimated at 15.5 billion yuan.
Flooding has disrupted traffic on 10 highways and more than 20 trains were delayed when a boat rammed into a pillar of a railway bridge.
Days of heavy rain has raised water in about 700 km of the Yangtze River from Jianli to Nanjing above the warning levels, but there are no reports of breaches on the main embankment, said Chen Guiya, an official with the Yangtze River Water Resources Commission.
Several small rivers and fish ponds in Hunan and Hubei have overflowed, inundating farmland and forcing the evacuation of tens of thousands of people.
Heavy rain was waning in the middle and lower reaches of Yangtze River on Tuesday and Wednesday, bringing respite to the region, but a new round of torrential rain is expected in the coming days.