Located in Xilin Gol League of Inner Mongolia Autonomous Region,the Xilinhot-Abaga volcanic cluster is in the centre of the Daxing’anling-Datong volcanic eruption belt.More than 300 Quaternary basaltic volcanoes of different types are developed in the volcanic eruption belt.Maars are found for the first time in the study area,with those in Haotewula in the southeast of Abagaqi,and Chelewula and Esigewula in the northwest of Abagaqi to be the most representative.They all are large in scale,with cone diameters generally 3~4km,with the largest up to 6.5km.The maars show intact structure,a similar two-ringed mountain landscape and obviously phased eruption which contained a vigorous phreatomagmatic explosion at the earlier stage,and weak magmatic explosion at the later stage,and basaltic lava effusion in the last stage.The eruption sequence reflects the interaction between magma and water,the change of intrusive speed and outflow rate of magma.The Middle Pleistocene deposits of sand and gravel in the valley are covered by basal surge deposits.The TL age of sandstone-shale “xenolith”which was found in the spatter deposits close to the crater is( 0.112 ± 0.0096) Ma,indicating that the eruption time of the Maars was the early Late Pleistocene. Located in Xilin Gol League of Inner Mongolia Autonomous Region, the Xilinhot-Abaga volcanic cluster is in the center of the Daxing’anling-Datong volcanic eruption belt. More than 300 Quaternary basaltic volcanoes of different types are developed in the volcanic eruption belt. Maars are found for the first time in the study area, with those in Haotewula in the southeast of Abagaqi, and Chelewula and Esigewula in the northwest of Abagaqi to be the most representative. They all are large in scale, with cone runs generally 3 ~ 4km with the largest up to 6.5km. The maars show intact structure, a similar two-ringed mountain landscape and obviously phased eruption which contained a vigorous phreatomagmatic explosion at the earlier stage, and weak magmatic explosion at the later stage, and basaltic lava effusion in the last stage. The eruption sequence reflects the interaction between magma and water, the change of intrusive speed and outflow rate of magma. The Middle Pleistocene deposits of sand and gr avel in the valley are covered by basal surge deposits. The TL age of sandstone-shale “xenolith” which was found in the spatter deposits close to the crater is (0.112 ± 0.0096) Ma, indicating that the eruption time of the Maars was the early Late Pleistocene.