The bus was carrying 69 people when it crossed into oncoming traffic and hit a freight truck on a motorway in eastern Jiangsu province on Saturday, the Yixing public security bureau said.
A preliminary investigation determined that the accident was caused by a flat tyre on the left front wheel of the bus, the bureau said in a statement, AFP reported.
Nine people were seriously injured, 26 were slightly hurt and one was discharged from hospital.
The Changchun-Shenzhen motorway reopened after eight hours of rescue work.
Deadly road accidents are common in China, where traffic regulations are often flouted or go unenforced. According to authorities, 58,000 people were killed in accidents across the country in 2015 alone.
Violations of traffic laws were blamed for nearly 90 percent of accidents that caused deaths or injuries that year.