The structural characteristics of poly (p-phenylenebenzobisthiazole) (PBT) film have been studied by X-ray diffraction method. The results of experiments show that PBT film which formed in liquid crystalline phase is high orientated. The molecular chains in the plane which perpendicular to the direction of orientation arrange in two-dimensions order while along the direction of orientation arrange in disorder. By annealing the PBT film

we found the regularity of the two-dimensions arrangement of molecular chains in the plane which perpen-dicular to the direction of orientation increases obviously and the distortion of lattice decreases.Moreover the benzene heterocyclic rings in the molecular chains along the orientation direction exibit cybotactic state and the diffraction pattern of X-ray showing the three-dimensions order appears. The angle between the normal line of the cybotactic plane and theorientation direc-tion is 29°.