Abstract: The willow and female waist have often been linked together in traditional Chinese poetry. This article tries to sort out the origin and development of this imaginary linkage, particularly its frequent appearance in Tang Poetry. The author holds that the dress styles and dance of Tang women easily revealed their slim waist and the large number of singer-dancers who closely associated with literati made slim waist a common presence. Willow trees were widely planted in Tang Dynasty, both in the public sphere and in private gardens. The common view of slim waist and the wide plantation of willow trees constituted the prerequisite conditions for the advent of this imaginary linkage. Moreover, the simultaneous presence of willows and waists at parting occasions, royal banquets and literati gatherings forms the necessary condition for the advent of this imaginary linkage. In Tang, particularly middle and late Tang, these conditions were fulfilled at the same time, which facilitated the frequent linkage of the two objects of the willow and the waist in Tang poetry.