Abstract: In the recent years, the researches in the life and medical field has gradually found that human is a super symbiont composed of human body and symbiotic microorganisms, especially intestinal flora. Here we proposed a quaternion vector model of human structure and function on the basis of "hunger sensation comes from gut flora" combined with mathematical and biological cybernetics. "Quaternion" was discovered in 1843 by Hamilton, an Irish physicist and mathematician, which led to a mathematical revolution. It is possible to obtain new discoveries about "what is human" by applying his ideas and principles to the field of life science in an interdisciplinary way and combining the knowledge of genetics, microbiology, physiology and anatomy. Specifically speaking, the quaternion model is used to analyze the human structure and function in this paper, that is \vec z=a+b\vec i+c\vec j+d\vec k. In this formula, the corresponding relationship in structure is \vec z(human body vector)=a(body scalar)+b\vec i(gut flora vector)+c\vec j(mitochondria vector)+d\vec k(human brain vector), the corresponding relationship in function is \vec z(holistic human)=a(human body for moving)+b\vec i(gut flora for eating)+c\vec j(mitochondrial for breathing)+d\vec k(human brain for thinking). It is equivalent to regarding the "human beings" as a unity composed of 1 scalar and 3 vectors. Therefore, we can get a new understanding of the human structure and function.