Because of the excellent concealment and environmental adaptability, animal robots play an important role in future wars or local conflicts. They may become the trump card to determine the outcome of battlefield. Aiming at the animal robots and their potential military application value, in this paper, the principles of animal robots are introduced at first, and then the research status of land animal robots, flying animal robots and underwater animal robots according to the differences of animal living environment is summarized. On this basis, the potential military application value of animal robots in approach reconnaissance, target guidance, target recognition, direct attack, and so on, is analyzed. The engineering problems in stimulation target, stimulation mode, biocompatibility, control device, wireless communication and energy supply, as well as future research directions are discussed. The advantages of animal robots are very obvious, but the technical requirements are also very high. At present, they are only in the initial stage, and there is still a long way to go in the future.