The East Mongolian Volcanic Area (EMVA) is the largest among the Late Mesozoic volcanic areas of the continental part of East Asia. Magmatic activity within EMVA can be traced from ~ 170 Ma to the start of the Cenozoic, however, the main activity cycle fell on the interval between 135 and 105 Ma. It was accompanied by rifting and the formation of elongated northeast system of grabens and sags filled by volcanic rocks. The largest volcanic outpouring occurred in the first half of the Early Cretaceous. In this activity phase mainly basaltic lavas were formed and acid volcanics culminated its. From the second half of the Early Cretaceous, only mafic volcanic rocks were formed. Alkaline basaltoids became dominant from the end of the Early Cretaceous and in the Late Cretaceous. Among the basic rocks of the EMVA, trachybasalts and basaltic trachyandesites are prevailed, alkaline basaltoids are subordinate. The geochemical characteristics of these rocks indicate the participation of two types of magmas issued from different mantle sources. One of them has affinity to the source of suprasubduction basalts (IAB), and the other is close to the source of intraplate basalts of the oceanic islands (OIB). Rocks with intermediate characteristics predominate, indicating the interaction of magmas or their sources during magma formation. The most common OIB-type rocks have (Th/Nb)PM ≤ 1. The IAB-type rocks have limited distribution and were formed mainly in the early stages of the EMVA evolution. The acid igneous rocks of the EMVA are mainly formed by crustal anatexis, as well as interacting of such anatectic melts with differentiates of basaltic magmas. A model is proposed for the formation of the EMVA in a complex geodynamic setting, determined by the influence of the mantle plume on the edge of the continent, developing in the regime of an active continental margin. Changes in the composition of magmatic rocks expressed as time-depended increasing role of OIB-type basaltoids are caused of evolution of the mantle plume magma within a subduction-modified mantle of the mantle wedge.