Abstract: To detect and recognize the weak underwater signals are difficult problems in pro-cessing underwater acoustic signals.This paper presents a,study to the chaotic phenomena of noises radiated from ship by analyzing phase space portraits,estimating Lyapunov exponents and calculating correlation dimension.It was found that there are chaotic attractors in this kind of signals,and different type of ship has different correlation dimension.This result may providea novel theoretic means for detecting and recognizing underwater targets.