Dolphin belongs to mammals, cetaceans, odontaceans and dolphins. It is a small cetacean, with nearly 62 species, distributed in all oceans of the world. It is 1.2 ~ 4.2 meters long and weighs 23 ~ 225 kilograms. Dolphins generally have sharp mouths, with about 10 1 fangs in the upper and lower jaws. They mainly feed on small fish, squid, shrimp and crabs. Dolphins like to live a "collective" life, and the number ranges from a few to hundreds. Dolphin's brain is the most developed except human, accounting for 1.7% of body weight, and it can complete various actions through training.