The meaning of “beside the seventh thoracic vertebra, there is a small heart” in Huangdi Neijing (Inner Canon of Huangdi) is discussed. Combined with the chapters of Gudu (Bone Measurement) in Lingshu (Miraculous Pivot), Beishu (Back-Shu Acupoints) in Lingshu, Cire in Suwen (Plain Questions) and other chapters, the meaning of the seventh thoracic vertebra is explained. It is considered that the “kidney acupoint” is the “seventh section” starting from the “phrenic acupoint”. Meanwhile, according to the symmetrically expression and figurative metaphor at the beginning of Cijin Lun in Suwen, it finds that the “small heart” refers to the two kidneys.