Negative thermal expansion material ZrW2O8 was synthesized by hydrothermal method. The prepared ZrW2O8 and the precursor were characterized by x-ray diffractometer, thermo-gravimetric/differential thermal analyzer, FT-IR spectrometer and scanning electron microscope. The results show that a single-phase ZrW2O8 can be synthesized when HCl concentration is as low as 4mol/L. ZrW2O8 was obtained through the precursor dehydration and debonding O-H bond. The dehydration reaction includes two stages. There is a sharp endothermic peak in the first stage of the dehydration reaction and the second stage is a slow endothermic process. A new phase appeared when the sintering temperature is above 600 °C. ZrW2O8 and the precursor have the same rod-like shape and grow up along a specific direction. The synthesized ZrW2O8 particles obtained from 4mol/L HCl appeared large size. It became much finer and the rod with multiple crystal face was easy to form when the concentration of HCl increased to 6~8 mol/L.