Abstract: According to historical data, the forest cover rate on the mountains of Baoding area was very high in the early years of the Ming Dynasty, and high-density forests and mountains were once as a natural barrier in the northern defense system. Since Yongle moved the capital to the north, the defense constructions in the mountains of Baoding were extremely frequent. As the key spot of the capital Peking, the largest and strongest defense construction happened in Zijingguan. Varied military engineering occupied a large area of forest, and logging a large number of trees for the daily life of soldiers occurred very often, resulting in a sharp decline in the areas of forest in the whole Ming Dynasty as well as the emergence of large area of wasteland around the Zijingguan in the late Ming Dynasty. Consequently, forest area decreased, soil erosion increasingly worsened, and floods in the downstream happened frequently. In the Ming Dynasty, forest protection always was in lower priority compared to military construction, thus ecological environment has been irreversibly damaged, and the negative effects influenced deeply on life of the later generations.