In electric power system， passerby or electric power operator frequently goes wrong to electric power danger zone. This paper brings forward a phonetic caution method using microwave induction technology. Microwave induction sensor is used to detect surrounding space， and the signal from microwave induction sensor is processed. The central processing unit can control phonetic caution circuit， then the phonetic annunciator accordingly achieves the phonetic caution effect to passerby or electric power operator who going wrong to electric power danger zone. The composition， working principle， using scope， generalizing and updating of the phonetic annunciator are discussed.