Abstract: This paper reports newly discovered Early Carboniferous volcanic rocks in Engeriyinpeng area of Sonid Left Banner, Inner Mongolia.LA-ICP-MS U-Pb zircon dating shows that the volcanic rocks has an age of 333.0 ±1.4Ma, which suggests that Baoligaomiao Formation was erupted in Early Carboniferous. Geochemical analysis shows that most of the samples are characterized by calc-alkaline rock series. All the acidic volcanic rocks fall into rhyolite area, two of the neutral volcanic rocks fall into trachyte area, other samples fall into dacite area, and all samples are characterized by alkaline rock series in the TAS diagram. All samples have similar characteristics of REE patterns which are characterized by medium total REE content (∑REE=110.6×10^-6~273.3×10^-6), significant fractionation of HREE and LREE (La/Yb)_N=2.39~5.31) and relatively strong negative Eu anomalies (δEu=0.48~0.65). The trace element geochemistry is characterized evidently by enrichment of LILE (Rb and Th), and strong depletion of HFSE (P, Ti, Nb and Ta). The ratios of Rb/Sr (0.50~6.64), Ti/Y (6.82~85.21) and Ti/Zr (2.27~19.71) all fall into the field of the earth's crust source. These characteristics indicate that the volcanic rocks might have originated from partial melting of the earth's crust, and they were formed in a subduction-related settings. Combined with the regional researching results and the previous research results, the authors hold that the Carboniferous volcanic rocks, together with other Early Carboniferous arc-related felsic magmatic rocks in the Erlianhot-Dongwu Banner region, constitute the magmatic arc caused by the northward subduction of Hegenshan Ocean.