With the progress in the research on global volcanoes, geologists have discovered volcanoes of Maars type with special genesis in most volcanic groups. Maars, characterized by low-relief, broad volcanic crater and low flat cone, are mainly composed of base surges with climbing bedding, parallel bedding, large low-angle cross-bedding and some other structures, thus being an important object for studying the evolution process of volcanic eruption. Many Maars with typical base surges have recently been discovered from Nuominhe, Arshan-Chaihe and Abaga volcanic clusters in eastern Inner Mongolia. Based on comprehensive field survey and available researches both in China and aboard, the authors summarized the geological features of the late Quaternary Maars in eastern Inner Mongolia by theories of volcanology and volcanic geology, including their distribution, products and typical structures. The activity of the volcano is divided into three stages:phreatomagmatic eruption stage dominated by base surges, magma eruption stage represented by fall-spatter deposits, and magma overflow stage with alkaline olivine basalt. These composite volcanoes were active in the late Pleistocene, whereas the Maars mainly erupted at early to middle stage stated above. The unique strata, volcanic product and regional tectonic structure all indicate that phreatomagmatic eruption was generated at the shallow depth. Based on the discussion of the genetic mechanism and evolution simulation, the authors infer that there exists an inherited relationship between Maars and other volcanoes, such as Strombolian and Hawaiian.