In this letter, a hierarchical extended multi-component decomposition method (ExMCSM) of polarimetric synthetic aperture radar interferometry (PolInSAR) is proposed. The target of this method is to overcome the overestimation of volume scattering (OVS) and to mitigate the mixed ambiguity of the scattering mechanism. In the proposed method, prior to the decomposition, orientation angle compensation (OAC), and helix angle compensation (HAC) are applied to the coherency matrix to reduce the complexity of the operation. The polarimetric interferometric similarity parameter (PISP) is used to refine the volume scattering models, and the optimal coherence magnitude ( ${\gamma _{\mathrm{ opt3}}}$ ) is used as a criterion for the adaptive selection of these volume scattering models. The efficiency of the proposed method is demonstrated using two different test sites. Experimental results demonstrate that the proposed method can effectively represent the scattering characteristics of the ambiguous regions.