The effect of pyrolytic temperature on the microstructure changes, mass loss and H/C ratio of polyarylacetylene was studied by thermal gravity analysis, element analysis and X ray diffraction. The results show that polyarylacetylene gives 84% char yield when pyrolysis at 900 ℃;with the increase of pyrolytic temperature, the ratio of H/C decreases and the carbon content and the degree of graphilization of pyrolytic sample increases. At the temperature range of 350~600 ℃, with the increase of pyrolytic temperature, the initial structure of polymer was destructed gradually; and when the pyrolytic temperature higher than 600 ℃, with the increase of pyrolytic temperature, a new structure was formed gradually.