Understanding the dynamic change in carbon sequestration in Larix forests plays an important role in maintaining the stability of the forest ecosystem in the Altay Mountains. Based on the continuous inventory data of forest resources during four periods (2001,2006,2011,2016), we estimated the carbon density, carbon storage, and productivity, and analyzed the temporal and spatial variation characteristics of Larix forest in the Altay Mountains using a one-element biomass model and an equation between biomass and productivity. At the same time, the climate response mechanism was discussed by the methods of standardized coefficient and factor analysis. The results show that (1) the carbon sequestration of the Larix forest showed a growth trend from 2001 to 2016, but the growth rate was not high. (2) The carbon storage in the Larix forest was in the order of Fuyun > Altay > Habahe, Qinghe > Buerjin > Fuhai; the carbon density and net primary productivity (NPP) were higher in the southeastern area than in the northwestern area. Vertical distribution showed that the carbon storage, carbon density, and NPP first increased and then decreased with elevation and were the highest on the north and northwest slopes. (3) The carbon density and productivity of the Larix forest increased with an increase in air temperature, and air temperature was the dominant climatic factor.