Abstract: Cobalt, as one of essential trace elements for animals, plays an important role in animal hematopoiesis, immunity, growth and reproductive performance, especially in microbes synthesis of vitamin BI2 for the ruminants. Also, cobalt can take more obvious effects with other trace elements. Cobalt deficiency will result in the degradation of animal productive performance so as to cause huge economic losses in animal husbandry. Therefore, with the depth of the scientific research, the important nutritional functions of cobalt have been also found gradually and attracted more attentions of people. The biological effects, the mechanisms of nutritional and deficiency disease, the relationship with other nutrients as well as the important role in animal nutrition were discussed in this paper.