Polarization photovoltaic effect is a unique character for an energy mate-rial with speciﬁc in-plane anisotropy. Especially, if the energy material has a direct bandgap close to 1.6 eV, it will efﬁciently absorb full sunlight spectrum with speciﬁc axial polarization. In this study, polarized microtransmittance measurements of GeS multilayer with polarization angles ranging from θ = 0° (E || a) [through 90° (E || b)] to θ = 180° (E || a) have been studied near band edge. The polarized absorption edge follows a sinusoidal variation of E(θ) = 1.6 + 0.05⋅|sin(θ)| eV with respect to the angle change of the polarized absorption spectra. This anisotropic optical response is well reproduced by ﬁrst-principles calculations based on a combined Green’s function technique, the GW–Bethe–Salpeter equation (BSE) approach. To characterize highly anisotropic band structure of layered GeS, polarized thermoreﬂectance measurement and ﬁrst-principles quasiparticle band-structure calculations are also carried out. The interband transitions belonging to E || a and E || b polari-zations are respectively identiﬁed. The polarized surface photovoltaic effects of a GeS Schottky solar cell are also tested. The special in-plane optical anisot-ropy (along a and perpendicular to the a axis) renders GeS owning highly bi-axial responsivity with respect to the c-plane photoelectric conversion.