We theoretically investigate the anisotropic plasmonic resonances in the proposed infrared absorber, which consists of stacked graphene-black phosphorus (BP) bilayers with dual absorption peaks. By combining the advantages of graphene and BP, stacked graphene-black phosphorus bilayers exhibit high absorption rates at both peaks and strong anisotropy. The loss mechanism is revealed deeply with electric field distributions, while the near field coupling between graphene and BP is discussed detailedly. Furthermore, by altering the corresponding doping levels of graphene and BP, each of the absorption bands can be independently tuned effectively. The angular dependence for oblique incidence is illustrated by performing a series of simulations. Besides, polarization-sensitivity for stacked graphene-BP bilayers (GBPBs) is also presented. Thus, our approach provides a theoretical and systematic guide for designing a variety of multi-resonant graphene-BP-based spatial absorbers, which show potentials in the applications of sensors and reflective polarizers.