Acoustic signal processing in shallow water environments is a challenging problem because of the presence of reverberation. Based on some models of reverberation, data from sensors array is pretreated to suppress reverberation. Considering reverberation as a sum of echoes of transmitted signal, the principal component inverse (PCI) algorithm is operated by deleting the largest singulars of data matrix, which is reconstructed by array data. However, the amount of calculation is very large because the construction of data matrices is complex and singular decomposition is needed. In this paper, the construction is simplified. As a result, computing quantity of PCI is reduced. After PCI-pretreatment, broadband direction-of-arrival is estimated by diagonal loading beamforming. According to a simulation which takes broadband linear modulated frequency signal as transmitted signal, with PCI-pretreatment the performance of DOA estimation can be improved.