Van der Waals heterostructures have an important potential for the rising self-powered photoelectrochemical photodetectors on account of their excellent photoelectric conversion functionality and environment friendly interfacial service transportation. By contemplating the band alignment, structural design, and progress optimization, the heterostructures of vertically oriented SnS2 with completely different densities on MoS2 nanosheets are designed and fabricated utilizing a two-step epitaxial progress methodology. In contrast with SnS2, MoS2, and low-density SnS2/MoS2 heterostructure, the high-density SnS2/MoS2 heterostructure displays largely enhanced self-powered photodetection performances akin to an enormous photocurrent density (~932.8 μA cm−2), a wonderful photoresponsivity (4.66 mA/W), and an ultrafast response/restoration time (3.6/6.4 ms) within the ultraviolet−seen vary. This spectacular enhancement of high-density SnS2/MoS2 photodetector is principally ascribed to the primarily improved cost switch and service transport of type-II band alignment heterostructure and the environment friendly mild absorption from the distinctive light-trapping construction. As well as, the photoelectrocatalytic water splitting efficiency of the high-density SnS2/MoS2 heterostructure additionally advantages from the type-II band alignment and the light-trapping construction. This work supplies invaluable inspiration for the design of two-dimensional optoelectronic and photoelectrochemical units with improved efficiency by the morphology and heterostructure design.