The morphology of spherulite and mat-crystal structure in PPTA films coagulated from pure sulfuric acid solutions under different conditions has been studied by light scattering method．Unlike flexible chain polymers，the molecules of PPTA may aggregate not only to form the spherulites．but also some anisotropic rod-like domains at the same coagula-tion conditions．The results of infrared dichroism indicate that molecules within mat-crystal strut-ture are highly oriented in the shearing direction (i.e．direction perpendicular to the band). According to the angular (angle bctween shearing direction and polarization direction of the analyzer) dependence of grating diffraction effect we suggest that the alternate change of brightness of paralleUy arranged bands in tile mat-crystal structure js primarily due to the slight difference in orientation direction of molecules within these bands．A method for calculating the number average long period (Pn) of the mat-crystal structure and the orientaticn of the bands from the d4ffraction pat-terns is proposed，and has been used successfully in characterization of PPTA films．Based on the light scattering studies of thin layers of the PPTA pure sulfuric acid solutions we have found that the mat．erystal structure is formed originally in the anisotropie PPTA solutions under shearing．After rapid coagulation of these layers the mat-crystal structure may be fetalned in the films obtained．