Volcanic rocks of Dahalajunshan Formation extensively occur along Kekesu River area in Western Tianshan Mountains. The authors studied zircon geochronology and geochemistry of the intermediate and basic lavas exposed in this area. Combined with the previous work on sequence stratigraphy of volcanic-sedimentary rocks, the authors hold that the volcanic rocks from Dahalajunshan Formation were formed in a rift environment related to the intense extension of the lithosphere after the final closure of the Paleozoic Tianshan Ocean.