Abstract: Abstract: Otindag sandy land and Hulun Buir sandy land belong to east Inner Mongolia and lie on the two sides of modern East Asian Monsoon (EAM) boundary. Based on optical stimulated luminescence (OSL) and 14C dating method combined with chemical elements analysis, regional paleoclimate was reconstructed. The results indicate that Otindag sandy land experienced three warm wet periods in the last deglaciation, Holocene optimum and Medieval warm period respectively. Whereas Hulun Buir sandy land only experienced the last two warm epochs. These periods were responses to the East Asian Summer Monsoon (EASM), roughly reflecting the EASM enhancement in two different degrees since the last deglaciation and the retreat process in the end of Holocene optimum. By contrast with previous studies, the EASM began to retreat at about 4 ka in east Inner Mongolia; the monsoon intensity was weaker in Medieval warm period, and the duration was short.