Abstract: Seismic signal generated on ground by moving person and vehicle target was sensed by MEMS accelerometer, then collected and processed by MSP430, achieving early-warming and target identification for ground targets. A method based on three times of the noise variance as the threshold value was proposed as to early-warming. A modified zero-crossing analysis was used to identify different kind of targets. The results show that person within 8 meters and vehicles within 20 meters away from the accelerometer can be detected and identified effectively. The correct identification rate can reach 85% or more. This algorithm is very simple and practical when processing signal collected by sensors with digital output.