West Junggar structural zone distributed in the south western of the Central Asian Orogenic Belt, It’s a key area for studying the evolution of the Paleo Asian Ocean. However, there are currently controversies over the tectonic evolution of the West Junggar tectonic zone in late Carboniferous. The newly discovered volcanic rocks from the Baiyanghe Formation in Early Permian probably can alleviate those controversies. Baiyanghe Formation volcanic rocks are mainly consist of basalts and the symbiotic subvolcanic rocks. It has angular unconformity relationship on the Early Permian Jiamuhe Formation with continental molasse sequence. In terms of geochemical compositions, the basalts are relatively high concentrations of Al2O3 and low concentrations of TiO2, they belong to the middle－low K calc-alkaline series. The ratio of ∑LREE/∑HREE ranges from 2.31 to 5.00. All the basalts of the Baiyanghe Formation are enriched in LREE without obviously Eu anomaly (δEu=0.99～1.29). Furthermore, they are enriched in light LILE, such as Ba, K, Sr. In addition, depleted in HFSE such as Nb, Ta, Zr, Hf and show the “TNT” negative anomaly. (206Pb/204Pb)i =17.924～18.000, (207Pb/204Pb)i =15.469～15.509, (208Pb/204Pb)i =37.737～37.879. εNd(t) = +5.93～+6.76, 87Sr/86Sr =0.703974～0.704299, It indicates that the source probably is the dehydration of subducted plate to produce the fluid result in metasomatic depleted mantle. These characteristics are consonant with the geochemical characteristics of late carboniferous marine island arc basalts, they have correlation in timeliness and extensity, and have the characteristics of homology, syngenesis and syntectonic background, it seems like excellent inheritance. The time of Baiyanghe Formation later than Jiamuhe Formation molasse, which confirms that Baiyanghe Formation basalts were erupted after the closure of the ocean basin, so it belongs to “Lagged arc” formation. Combining with previous researches and the regional geological background, the ocean basin was closed in Late Carboniferous, nevertheless, the deeply subduction continued until produced the Baiyanghe Formation in Early Permian. In the process of ocean-continent transition, it experienced a unique tectonic evolution process of “Lagged arc”. The “Lagged arc” formation volcanic rocks provide essential constraints for the suture location of the Paleo-Asian Ocean and the tectonic evolution process in West Junggar.