Abstract: Towed line array is recently a very active topic in the field of sonar signal processing.It is possible to use the adaptive line enhancer in the signal processing system of a towed line array.It is shown that the system gain of an adaptive line enhancer in which the LMS iterative algorithm is used,is related to the input signal to noise ratio due to the presence of iterative noise.The line enhancer would be useless,if the platform noise has not been cancelled.A cascade architecture of adaptive noise canceller and adaptive line enhancer is proposed in this paper.The platform noise,as an strong interference is cancelled by the adaptive noise canceller.So that the sinusoidal components in the output signal are enhanced by the followed line enhancer.It is possible to detect the weak line spectrum components from strong noise background.The block diagram of such cascade system and the performance analysis are given.The system simulation shows a good agreement with the theoretical analysis.