The present disclosure provides a smart ear tag, which has the characteristics of miniaturization and multi-function, and can collect animal vital signs, such as the animal's body temperature, heart rate, exercise amount and other information, and can also collect environmental temperature and humidity information. When the smart ear tag is used Applied on the animal's ear, the smart ear tag can continuously collect the animal's body temperature, heart rate, and exercise, and at the same time collect environmental temperature and humidity information, and use it to determine or predict the animal's eating time or rumination time, and then can according to the eating time or The rumination time judges the physiological state of the animal, and then the animal's diet structure, feeding time, etc. can be adjusted in time, and the ambient temperature and humidity can also be adjusted accordingly.