The bus had been travelling from the central province of Anhui when it plunged from the bridge in Guizhou province into a 10-meter-deep crevice, Xinhua news agency reported.
A number of people were injured, many seriously, in the accident. Several parts of Guizhou province were hit by heavy snow on Wednesday, which led to wet and slippery roads and caused several road accidents.
In another accident, eight people were killed and 13 others were injured when a coach collided with a truck in southwestern Yunnan province last night.
The accident occurred on the expressway in Huize county of Qujing city. The accidents marks the third deadly bus crash to occur in China in just two days.
Thirteen people died and 41 others were injured on Tuesday when a heavy-duty truck collided with a coach on the Shanghai-Kunming expressway in central China's Hunan province.
The accidents occurred just before the annual Chinese New Year travel rush. Road safety is a serious problem in China, with many accidents caused by poorly maintained roads and bad driving habits.