Abstract: The Karamaili ophiolite is one of the representative ophiolites in the Central Asian Orogenic Belt (CAOB). The time limits of the opening and closure of the Karamaili oceanic basin remain a key problem due to the lack of high accuracy isotopic ages. The LA-ICP-MS zircon U-Th-Pb dating of diabase in Karamaili ophiolite yielded an age of 416.7±3.2 Ma, recording the generation of the oceanic crust. Sedimentary rocks conformably overlies Karamaili ophiolite. The 343.0±5.0Ma zircon U-Pb age from the tuff overlying the strata constrains the upper limit of the emplacement age of the Karamaili ophiolite and suggests that the sedimentary cover is Early Carboniferous in age. Therefore these ages indicate that the Karamaili oceanic basin was opened in the Lochkovian stage during Early Devonian and closed before the Tourmaisian stage during Late Carboniferous. Accurate constraints on the formation and emplacement age of Karamaili ophiolite provide important constraints for the tectonic evolution of the eastern Junggar Orogenic Belt and the tectonic framework of the CAOB during the Palezoic period.