The study of vegetation and climate changes of ecological sensitive area since 5000 years,especially the period of the Little Ice Age and the Medieval Warm Period will contribute to understanding how the ecosystem respond to climate change. A sediment sequence (1.2m in depth) from the Anguli-Nuur Lake (41°18'~41024'N,114°20' ~ 114°27'E; 1313m a.s.l.),which is one of the largest inland lakes in the transition zone between a semi- humid and semi-arid climate parallel to the present limit of the southeast monsoon along the southeastern Inner Mongolia Plateau in the Bashang Plateau of Hebei Province, was selected to reconstruct the history of vegetation and climate since 5000cal.a B.P., based on pollen analysis, sediment grain size and major chemical elements analysis, combining with 14C dating data. Totally 94 sample were collected, and the pollen analysis results indicated that a total of 49091 pollen and spore grains (more than 435 grains in each sample) and 78 pollen types, including 21 arboreal and shrub pollen types, 47 herbaceous types and 10 fern types were identified. In different period,pollen concentrations, sediment grain size and ratios of chemical elements changes obviously. From 5030 cal.a B.P. to 1070 cal.a B.P., the pollen concentrations are more than 6000 grains/g, and the drought index((K + Na+Ca+Mg)/(Fe + Mn)) is less than 3.42,alkali index ((CaO + K_2O + Na_2O)/Al_2O_3) are lower than 1.44 and CaO/MgO are values lower than 0.73 respectively, indicating relative humid climate and relative stable water area and depth. In the Medieval Warm Period (1070 ~ 620 cal.a B.P.),the average pollen concentrations decreased below 3200grains/g and the average grain diameter and variable amplitude enlarged, in the meantime, the drought index value (average 3.60) and alkali index value (average 1.53) increased rapidly, suggesting that the regional climate not only become very unstable but the drought were enhanced. In the Little Ice Age(620cal.a B.P. to 45cal.a B.P.),the pollen concentrations averagely decreased below 2400 grains/g, the drought index and alkali index values reach to the maximum in all sequence, indicating the drought were enhanced further more. The maximum of the Little Ice Age is from 490cal.a B.P. to 250cal.a B.P., when the pollen concentrations are less than 1000 grains/g,combined with the highest drought index value (average 3.63) and alkali index value (average 1.67). Thus it can be seen that the lake has been shrinking since 5000cal.a B.P.,and the drought trend has been become more and more serious, especially since 1000cal.a B.P. Since 45cal.a B.P., the climate has become a little warm and wet,but the content of the lake carbonate got much higher than before,represented by higher CaO/MgO values (more than 1), suggesting that the lake areas and depth continue shrink. That should be mainly affected by serious human activities and the reconstruction of reservoir in the river upstream. The high content of Pinus and Picea in pollen assemblages should mainly come from the mountains located in the south-east of Bashang Plateau,and then transport to the lake by inflow river water.