According to the requirement of low power consumption of modern intelligent ammunition system, a low power consumption early warning system circuit based on seismic signal is proposed. Through the analysis of the characteristics of the seismic wave, the seismic sensor of the early warning system is selected reasonably. Based on the principle of adaptive floating threshold and target passing characteristics extraction, a low power hardware circuit is designed to realize the seismic early warning system, and the system structure block diagram and the working principle of the main circuit are given. The test results show that the circuit system has the characteristics of low power consumption (< 5 mW), low false alarm rate (< 6 times/24 h) and long early warning distance (armored target 350 m), and can resist the shock interference such as battlefield explosion.