Abstract: The modular population of Picea mongolica is studied in this paper.The results showed that:(1) Root of Picea mongolica grows rapidest in order for adapting the drought environment;(2) Needle life changes with the tree age,needle life of 40 year-old tree is longer that of 200 year-old tree;(3) As to branches,there are relationships between branches number and branches age,those are:B₄₀=2682.5e-0.6958A (R²=0.9553),B₂₀₀=5807.5e-1.3112A (R²=0.9603);(4) The ratio of male flowers and female flowers increases rapidly with tree age;(5) There is great significance of cones ratio in different layers and directions with age.The tree is older,the ratio is larger in middle layer,and the ratio is fewer in upper layer.The ratio is larger in southern and western directions,and it is fewer in northern and eastern directions;(6) As far as crown type and architecture type is concerned,the radius of crown in eastern direction is longest,that in western direction is shortest.Branches number,branches length,small branches number,and branches angle increase with tree age,but length of small branches decreases.The results showed that Picea mongolica could adapt to the drought environment.Modular dynamics and structure of Picea mongolica result from long-term natural selection and adaptation to the drought environment.