At least 13 other people are missing in floods that have ravaged mountain districts of six provinces and autonomous regions, forcing tens of thousands from their homes and causing major damage to buildings and crops.
Among the dead were 16 people killed in the collapse of a nine-story building in the city of Guiyang following a landslide.
The Guangxi regional government said another 21 kindergarten students were sent to the hospital in the school bus accident on Friday, with three listed in serious condition. The bus was licensed to carry 11 people, but had a total of 26 on board.
The driver, teachers and school administrators have been taken into custody, the government said. Overloaded buses have been involved in accidents killing scores of children in recent years as local schools are closed and consolidated into larger campuses farther away from the children's village homes.
Six people were killed in the central province of Hunan when a bus skidded into a guardrail and overturned.
Seasonal rains cause major flooding around China almost every year. The worst in recent history was in 1998, when 4,150 people died, most of them along the Yangtze River.
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