Abstract: Maar- type volcanoes are easily buried and not being recognized. They are different from volcanoes with cone shape commonly above surface, but characteristics of negative topography, circular or elliptical overlooked, small area, and distributed in highly dense clusters. In the northern part of Zhuozi County, Inner Mongolia, there exist such maars, which are the largest in scale and with the best preservation in the world. Making further study of them will supplement understanding of the negative terrain to geoscience field of our country, research on the Quaternary volcanic geology, and promote the local tourism.