The properties of carbon fibers made from PAN are controlled by precursor manufacture and heat treatment conditions. This work is concerned with the studies of morphological change of high molecular delight PAN film during heat treatment process with drawing conditions. The effect of heat treatment on the dynamic mechanical properties of PAN film was investigated in connection with the change of the mechanical loss tangent(tan) peak which may be attributed to cyclization procedure. The decrease of tan peak intensity was found to be related with the drawing condition. It is considered that the degree of the decrease of tn6 peak intensity may be due to the difference of chemical reaction and molecular motion in the amorphous region. The extent of morphological changes is also found to depend on the draw ratio. From a consideration of apparent activation energy of absorption(a2) and ammaticity index, it may be concluded that the structure of amorphous region is also a factor iuluencing the degree of cyclization.