Solar-blind ultraviolet photodetectors based on two-dimensional van der Waals heterostructures have emerged as indispensable components for high-precision warning systems, environmental monitoring systems, information encryption, and optical communication. However, the widespread use of solar-blind ultraviolet photodetectors is still constrained by the simultaneous lack of ultralow dark current, high specific photoresponse, sub-microsecond response time, and intrinsic polarization-sensitive photoresponse. Herein, a dual-heterostructure field-effect transistor composed of the ultra-wide bandgap semiconductor GaPS₄ and WS₂ nanosheets was fabricated. The WS₂/GaPS₄ dual-heterostructure devices exhibit high spike barriers at the dual-heterostructure interface owing to type-I band alignment, which can completely suppress charge transfer. Furthermore, the device exhibits an outstanding performance in the solar-blind ultraviolet (UV) region, stemming from the fast carrier separation and transfer enabled by the built-in electric fields at the dual-heterostructure interface. Critically, the two-fold rotational symmetry (C₂) of GaPS₄ breaks the original three-fold rotational symmetry (C₃) of WS₂ to simultaneously achieve unexpected linearly polarized Raman and anisotropic absorptions at the heterostructure interface. Moreover, the WS₂/GaPS₄ dual-heterostructure photodetector possesses high-resolution polarization imaging capability under 255 nm illumination owing to dichroic ratios as high as 3.4. These results suggest that the novel two-dimensional dual-heterostructure provides a foundation for developing next-generation polarization-sensitive multifunctional photodetectors.