The phase decomposition of single ZrW2O8 was investigated by sintering at different temperatures. After quenching, the decomposition of ZrW2O8 was estimated by the phase analysis and the phase decomposition mechanism was discussed combining the solid phase transition theories and crystallographic theories. Then the solid phase synthesis method was used to investigate the influences of the sintering temperatures and cooling ways on the synthetic ratio of ZrW2O8. The results showed that the phase decomposition temperature region is 780~1108 °C and ZrW2O8 can exist steadily in the form of metastable state below 770 °C. The solid phase synthesis of ZrW2O8 occurred above 1108 °C and the maximum synthetic ratio was obtained when the sintering temperature was 1200 °C and water cooling way was adopted.