The bus, was carrying a group of German tourists.
The accident took place on a pivotal expressway linking Beijing with Shanghai, police authorities in Tianjin said.
The tour group was organised by the Beijing-based China Youth Travel Service. It was also unclear how many people were traveling in the bus.
Witnesses said they saw a few people escaped from the flames, state-run Xinhua news agency reported.
A photo posted by witnesses on the web showed the whole vehicle was engulfed in flames and dark smoke.
The municipal government of Tianjin has ordered immediate treatment of the injured.