Abstract: The significantly weakened precipitation in the western quadrant of tropical cyclone DOUG during its moving along the coast of East China was mainly due to its entirely asymmetric structure. This paper analyses the cause and evolution of the inner and outer asymmetric structures. The outer asymmetry was caused by the distribution of large scale synoptic systems with high pressure in east and low pressure in west to the cyclone. The inner asymmetry was due to the developing of a middle β-scale divergence and subsidence system. The two asymmetries for medindependenly, while the development and movement of the inner asymmetry stimulated the further development of the outer asymmetry. And the inner asymmetry's approaching to the outer asymmetry and meeting with it caused the entirely asymmetric structure of the whole cyclone.