The radiated noise of ships involves strong low-frequency line spectrum, which is greatly related with the
working states of auxiliary equipment and the rotation of propeller, and then regarded as the important basis in feature
extraction of ships. Moreover, the stochastic resonance has special advantages in the extraction of weak signal. Aiming at
the multi-frequency components in radiated noise of the ship with four-blade propeller, and the characteristic without
adiabatic approximation assumption, a sweep-frequency stochastic resonance detection system is established in this paper.
Meanwhile, a kind of detection method on multi-frequency signal with partitioning large parameters is proposed, in order
to identify the components of low-frequency line spectrum in radiated noise of ship. The analysis and simulation results
present that, under the strong noise background, the proposed method can still effectively detect the low-frequency line
spectrum, which lays the solid foundation for the subsequent target recognition and speed estimation of the ship.