High-purity flower-like MoS2 microspheres have been successfully synthesized by hydrothermal method using Na2MoO4 and CH3CSNH2 as precursors, and H4O40SiW12 as an additive. Samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). XRD and EDS patterns show that the as-prepared samples are MoS2, which have good crystallinity with a well-stacked layered structure. SEM images show that the as-prepared MoS2 are composed of flower-like microspheres with a mean diameter about 300 nm, the structures of which are constructed from dozens of hundreds of MoS2 nano-sheet with a thickness of several nanometers. It is also found that the silicotungstic acid plays an important role in the formation of the flower-like MoS2 microspheres, which could affect the size and morphology of the MoS2. Flower-like MoS2 is not found in the as-prepared product without adding silicotungstic acid. A formation mechanism of MoS2 microspheres is tentatively given.