Located in the southern margin of Tuha basin within the East Tianshan Mountains, Dananhu arc is famous for hosting Tuwu porphyry Cu deposits. It is important for us to deepen our understanding of the genesis of porphyry deposits and the tectonic evolution in the whole East Tianshan area. Based on detailed geological mapping, the authors recognized four lithostratigraphic associations in the Carboniferous Dananhu arc belt within the East Tianshan Mountains, i.e., the Lower Carboniferous Xiaorequanzi Formation consisting mainly of volcanic rocks, the Upper Carboniferous Dikan'er Formation composed of clastic rocks intercalated with carbonate, the Upper Carboniferous Qi'eshan Formation comprising volcanic rocks, and the Upper Carboniferous Qishan Formation of clastic and carbonate rocks. Their rock associations, geochemistry, fossils and spatial relationship together with previously published geochronological data suggest that the previously-thought Dananhu arc is actually made of arc volcanic rocks, back-arc basin sediments and remnant oceanic basin sediments, which are associated with the above-mentioned four units respectively. Thus, the tectonic and evolution framework has been established in association with regional studies. There existed at least two ocean-continent transformation stages (i.e., Late Devonian and Late Carboniferous) in the East Tianshan Mountains in Late Paleozoic. The marine deposit of Early Carboniferous Xiaorequanzi volcanic rocks was formed by ocean-ocean subduction in the Kangur Ocean far away from the Devonian active continental margin. The collision between marine volcanic rocks and the Tarim active continental margin (central Tianshan block) formed the Late Carboniferous remnant oceanic basin together with the subduction polarity reversal. The northern ocean basin began the S-dipping subduction towards the Early Carboniferous volcanic rocks and formed the Late Carboniferous Qi'eshan volcanic arc and Qishan back-arc basin. The final collision suture is Dacaotan fault between Tarim plate and Dananhu arc. The Carboniferous lithologic associations of Dananhu arc indicate that the East Tianshan Mountains may represent a complex archipelago-ocean basin, and this orogeny involved fore-arc accretion and back-arc basin closure during the whole orogenic process. Juxtaposition of different tectonic units implies that the East Tianshan Mountains orogeny was probably a multiple accretionary orogenic process.