In order to study the influence mechanism of heat treatment and heterostructures on the photoelectrochemical effect of WO₃, monoclinic WO₃ nanoflowers were synthesized by low-temperature solvothermal method. The active crystal fact, grain size and crystallinity of WO₃ were controlled by heat treatment. Furthermore, WO₃/CdS/α-S heterojunction was obtained by modified chemical bath deposition, and the concentration effect of its photoelectrochemical performance was studied. The results show that the (200) crystal plane with photoelectrochemical activity is the main exposed crystal plane of WO₃, and the proportion of the exposed crystal plane increases with the heat treatment temperature increasing. The WO₃ nanoflower treated at 350 ℃ showed the highest photoresponse current. By constructing WO₃/CdS/α-S heterojunction, the material's absorption in the visible light region is enhanced, and the overall efficiency of photo-generated carrier separation is improved by sacrificing a small amount of carriers, which promotes the macroelectronic chemical effects of WO₃.