The formation and evolution of the South Tianshan Mountains—Beishan Mountains—Solonker—Changchun Suture, as the final closure position of the Paleo-Asian Ocean, has been the focus of research of the Central Asian Orogenic Belt. Studies on the formation age and subduction polarity of this suture zone can help us to reveal the accretionary and evolutionary history of the Central Asian Orogenic Belt and provide theoretical support for the establishment of a tectonic evolutionary model of the Paleo-Asian Ocean. In this paper, the South Tianshan Mountains —Beishan Mountains —Solonker—Changchun Suture is divided into four segments based on the differences in geotectonic setting, rock composition, closure mode and closure era, and they are, from west to east: the South Tianshan Suture, the Beishan Suture, the Solonker—Changchun Suture, and the Changchun—Yanji Suture. The South Tianshan Suture is located in the western section of this suture zone and is a result of the northward subduction of the Tarim block, which collapsed with the Kazakhstan—Yili block, and it was formed in the Late Carboniferous based on the evidences of high-pressure metamorphic age, intrusive dike and unconformity cover, etc. The Beishan Suture is located in the middle section, formed during the northward subduction of Dunhuang and Alxa blocks, which collapsed with the Tuva—Mongolia block, and it was formed in the Early—Middle Permian based on the chronological evidences of the ophiolites. The two ophiolite belts at the northern margin of the Alxa block, as the connecting belt between the Beishan Suture and the Solonker—Changchun Suture, represent the suture zone and the post-arc basin formed during the closure process of the Paleo-Asian Ocean, and they were formed in the middle Permian—early Late Permian. The Solonker—Changchun Suture is located in the middle—eastern section, where the Paleo-Asian Ocean underwent simultaneous southward and northward subduction in both directions, and the amalgamation of two sides was completed in the Middle Permian—Early Triassic. The Changchun—Yanji Suture was formed during the amalgamation between the North China Craton and the Jiamusi—Khanka block around the Middle Triassic, and is 20~30 Ma later than the formation age of the Solonker—Changchun Suture (270~250 Ma), Therefore, these two sutures have significantly different formation age and tectonic setting, and the Changchun—Yanji Suture is not part of the eastern extension of the Solonker—Changchun Suture. The Paleo-Asian Ocean evolved in four stages along the South Tianshan Mountains —Beishan Mountains —Solonker—Changchun suture, and the closure age gradually become younger from west to east, and the whole process lasted from the Late Carboniferous to Triassic, in which the Changchun—Yanji suture recorded the geological process of superposition and transformation between the Paleo-Asian Ocean tectonic domain and the Paleo-Pacific Ocean tectonic domain.