The preparation and optoelectronic properties of WS2-MoS2 vertical heterostructure were mainly studied. Molybdenum oxide (MoO3), tungsten oxide (WO3) and sulfur powder (S) were employed as reactants, and then high quality WS2-MoS2 vertical heterostructures were prepared by using an improved one-step chemical vapor deposition method (CVD). Raman spectroscopy (Raman), photoluminescence spectroscopy (PL), optical microscope (OM), atomic force microscope (AFM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and other related devices were used to characterize the morphology and element composition of the heterostructures. At last, the photodetector based on WS2-MoS2 vertical heterostructure was produced, and the photoelectric characteristics of the fabricated device including the output characteristic curve, transfer characteristic curve and photocurrent curve were measured. The test results show that the photodetector based on WS2-MoS2 vertical heterostructure exhibits wonderful photoresponse characteristics under the 532 nm laser mode. It obviously means that the photodetector based on WS2-MoS2 vertical heterostructure can be applied to the preparation of high-efficiency optoelectronic devices and have broad application prospects in the field of microelectronics.