The bus caught fire this morning when it was passing by a primary school at the northern part of Guiyang City, the provincial capital.
The fire has been put out and the injured have been hospitalised.
Pictures posted on China's Twitter-like service Weibo showed the vehicle was engulfed in flames with thick black smoke surging from it.
Firemen later doused the burning vehicle, state-run Xinhua news agency reported.
At least 50 passengers were on the bus and some of them got off in time, witnesses said.