In multicomponent surveys, the travel path of seismic waves from the subface interfaces to geophones may not be vertical to the ground; consequently, vertical and horizontal geophones receive mixed wavefields comprising P- and S-waves. Vector separation of wavefields is crucial for subsequent imaging and shear wave splitting analyses. However, conventional methods cannot address the nonlinear polarization of pure wave and can also produce incorrect results due to the presence of dipping interface. To address the above issues, we propose a vector wavefield separation method based on the slope of events and polarizability. The proposed method calculates the slope of the events for determining the propagation direction of the wavefield. The polarizability is used to evaluate whether the resulting wavefield is purely composed of one type of body wave, while the wavefield type is determined based on the angle between the polarization and propagation directions. When the wavefield is mixed, P/S separation is realized based on vector decomposition in an affine coordinate system optimized by the propagation direction. We use both numerical and field data to demonstrate the effectiveness and applicability of the proposed method. The numerical example confirms that the proposed method yields more accurate results than the conventional vector decomposition method. The field data application also indicates that the new method can effectively resolve the P- and S-waves from the noisy seismic wavefield.