Amphioxus is an insignificant animal, but it is an animal in the middle of evolution from lower invertebrates to higher vertebrates, and it is also a model of vertebrate ancestors. The feeding and excreting functions of amphioxus are all like invertebrates, but the vascular system, respiratory system, nervous system and embryogenesis all look like vertebrates. Moreover, it can be seen biochemically that it has all the creatine phosphate substances of vertebrates, but not all the hemoglobin and iron compounds of vertebrates. Amphioxus contains a special vanadium element. Therefore, no matter from the aspects of morphology, physiology, biochemistry and genetics, it shows that it is a transitional animal and a witness to the evolution from invertebrates to vertebrates. Because amphioxus has no spine, it is not easy to leave fossil traces, but the above is enough to show that amphioxus is a living witness. Therefore, both teaching and scientific research are very needed materials; In addition, it is a delicious food with rich nutrition.