Sporopollen, archaeology and historical documents all showed that during the Pre-Qin Period and Han dynasties, the northern region of China was covered with a wide range of forests.After the Spring and Autumn Period, the temperature fluctuation happened in most area of Northern China led to the change in species composition.From the Spring and Autumn Period to the Eastern Han Dynasty, the proportion of coniferous forest increased due to the dropped temperature, while broadleaved deciduous forest lost its size in the northern China.At the same time, the distribution range of forests became smaller.In Huang-Huai-Hai Plain, the broadleaved trees and the coniferous trees showed the growth and decline successively; there was no forest growing on the loess plateau, and the valley and hilly area were mainly covered with mixed forest dominated by broad-leaved trees.In addition to the climate factors, human activities have also affected the changes of natural vegetation.The economic, political and military activities during Qin and Han dynasties seriously damaged the forests and trees in northern China except for the northeastern China where the nature forests have been well preserved.