In order to improve the detection probability of seismic wave signals in low SNR environment, combining with adaptive line spectrum enhancement technology, this paper proposes a new realtime detection algorithm for ship seismic wave signals based on sliding power spectrum. Firstly, the signal is processed by adaptive line spectrum enhancement technology, then the power spectrum estimation is performed on the processed signal, the average power in a frequency band is selected as the detection feature quantity, and the corresponding adaptive detection threshold operator is designed. Finally, realtime detection of ship seismic wave signals is completed according to certain detection rules. The measured data show that the detection algorithm can effectively accomplish target detection with low signaltonoise ratio, and the detection probability reaches 93% when the signaltonoise ratio is -15 dB.