The study carried out the isotopic geochronology and geochemistry analysis of volcanic rocks revealed by the drilling in Suhongtu Depression Ying’e Basin to determine the formation age and the petro- genesis and tectonic environment. Zircon LA- ICP- MS U- Pb dating yields the age of 131. 8±5. 9 ~ 132. 6±0. 7Ma, indicating the rocks crystallized in Early Cretaceous. Its age is similar to or slightly later than that of the volcanic rocks of the Bayingebi Formation in the Chagan Sag, and different from that of the Suhongtu Formation of the Low Cretaceous in the region. This indicates that there were multiple periods of volcanic eruption in the Early Cretaceous, which occurred along Engerwusu fault at the same time or extended the southwest, were essentially independent of the northeastern extension of Altun fault. The Bayinggebi Formation volcanic rocks in the study area are mainly sub- alkaline basaltic andesite (SiO2 contents of 55. 97%~56. 37%), and characterized by high TiO2 (2. 10%~2. 35%), low MgO (0. 93%~1. 47%) and low Na2O+K2O (3. 17%~6. 49%). High ΣREE (352. 39 10-6~555. 5 10-6), distinct high fractionation of LREE and HREE, weak Eu nagtetive anomalies (δEu=0. 78~0. 85）, enrichment of large ion lithophile elements (e. g. Rb, Ba, Th), depletion of high field strength elements (e. g. Nb, Ta, Ti) and compatible elements (e. g. Ni, Cr), suggest that the volcanic rocks are characteristic of continental intraplate and continent margin, which are different from those of the Suhongtu Group volcanic rocks. Combined with the regional tectonic evolution and spatial distribution of volcanic rocks, the study suggests that the volcanic rocks of Bayingebi Group and Suhongtu Group were generated in response to within- plate extension, lithosphere thinning and the reaction of the Engerwusu fault, but the two had different magmatic sources. The Bayingebi Formation volcanic rocks show the characteristic of island- arc basalts, and this may result from that mantle area was affected by fluids brought by the early subduction. The volcanic rocks of the Bayingebi and Suhongtu groups had not suffered the crustal contamination during the magma went up, but the Bayingebi Formation volcanic rocks are characterized by distinct crystallization fractionation between mafic minerals and plagioclase, with the degree of the crystallization fractionation higher than that of the Suhongtu Formation volcanic rock.