The Tianchi volcano, Changbai Mountains, a polygenetic central volcano, is one of the most i mp ortan t active volcanoes with potential hazerds in China.In structure the volcano is c omposed of a basalt shield, a trachyte composite cone, a nd a comendite ignimbrite sheet. It is estimated that the maximum eruption colum n height is 25 km and that the maximum column width is about 13 km in radius.The caldera collapse experienced at least four phases during the composit econeforming and ignimbriteforming eruptions. A preliminary volcanic hazar ds assessment of the Tianchi volcano is also done in the paper.