Focusing on detection technology for autonomous underwater detection device which found marine target which radiated noise signal submerged in background noise, chaotic detector based on Duffing oscillator is researched. In this paper, the Duffing oscillator and chaotic detector based on Duffing oscillator are described. Through numerical simulation and theoretical analysis, it is proved that the detector can detect the underwater target radiated noise under the marine noise, even if the statistical characteristics of the features of target signal and background noise are unknown.