This paper poses an active underwater broadband sound absorption method, in which a piece of PVDF piezocomposite smart material is used as the absorption material. A adaptive feedforward control system has been construct based on the filter-X LMS Algorithm. A kind of easy to implement in engineering method for secondary path modeling, based on the Delay-LMS algorithm, has been studied. The reference signal and error signal of the control system are received through separating the incident and the reflection sound pressure from out of the acoustic field using the digital time delay system. The experimental research of active duct noise control in the the pulse tube is accomplished. It is shown that the PVDF piezocomposite smart material can absorb almost all of the low frequency incident sound pressure with active control.