Altay is an important part of the Central Asian Orogenic Belt, and also the largest accretion orogen in the world. At present, scholars both in China and abroad are focusing their Altay studies on the evolution of various stages of orogenic movements as well as geochemical and geochronological time constraints on the orogenic activities. In contrast, the study of the Mesozoic-Cenozoic cooling history is relatively insufficient. To carry out the researches on the cooling as well as denudation and exposure history of the post-orogenic stage of the Altay orogenic belt is of great importance in the in-depth understanding of the formation of a large mountain range after the evolutionary stage. Researches on the post-orogenic uplift of the cooling as well as denudation and exposure history about Altay orogen are of great significance in that it make researchers obtain in-depth understanding of the formation of a large mountain range after the evolutionary stage. With the improvement of the fission track analysis technology, fission-track thermochronology represented by apatite has become the effective means for revealing the denudation and exposure age and speed of orogenic activity as well as the evolution of tectonic, topographic and thermal history. Low-temperature chronology records rock movement information of the upper crust within a few kilometers and on a million-year scale, and thus offers a good choice for the quantitative recovery of ancient orogenic terrain. This paper discusses uplifting-denudation and exposure history and paleotopographic reconstruction of this region based on fission track technology. AFT data from 11 samples show that the AFTA range from 99.2 Ma to 43.7 Ma. The average denudation and exposure rate has been 0.050 mm/ma since Late Cretaceous. Thermal history modeling results show that there have been multi-phase cooling and denudation and exposure evolutions since the Cretaceous period in the south margin of the Altay Mountains. From Early Cretaceous to Late Cretaceous (about 120～50 Ma), the denudation and exposure rate was 0.044 mm/a, and from Late Cretaceous to Eocene (about 75-70～50 Ma), the denudation and exposure rate was 0.070 mm/a. Since the Miocene (about 20-15 Ma～Present), the denudation and exposure rate has been 0.081 mm/a (the denudation and exposure rate was obtained from three methods, i.e., the age-closure temperature method, the cooling curve simulation and the age-elevation method). Early Cretaceous tectonic uplift of the Altay Mountains was contemporaneous with the final closure of the Mongol-Okhotsk Ocean, and the convergence and eventual collision of the Siberian and North China (Sino-Korean)/Mongolian continents. Tectonic activities from Late Cretaceous to Eocene were affected by long-distance effects of Lhasa block and Kohistan-Dras arc accretion. Rapid uplift since the Miocene may be related to distant effects of India-Eurasia convergence. Low-temperature thermochronology can be used to conduct paleotopographic reconstruction, and the specific process is shown as follows: First, the cooling history of rock samples is remolded. Then, the amount of stratigraphic erosion is estimated through temperature gradient. Finally, such affecting factors as balance role, climate and tectonics are considered. Paleotopographic reconstruction of the study area shows that the average denudation and exposure highness from Cretaceous up till now is about 5 km, while paleoelevation has been decreased by about 0.8 km. Cretaceous-Cenozoic paleoelevation of the south range of Altay Mountains has tended to decrease except for a stable period of 50～17.5 Ma.