The vehicle “suddenly caught fire” on Tuesday morning near a public square in Yinchuan, officials in the capital of the remote Ningxia region said on a verified social media account.
The cause of the blaze was still being investigated, the post said, adding that 31 people were being treated in hospital.
The incident happened at about 7am.
A press officer at the Ningxia fire department said firefighters put out the fire in 10 minutes, AFP reported.
Traffic accidents are relatively common in China where safety standards are often lax.
There have been several bus fires in recent years in China.
In 2013 a suicidal man started a fire on a bus in eastern China that killed 47 people including himself, state media said.
The blazes are often blamed on the mentally ill or people who are seeking revenge against society.