A crystal structure of triphenodithiazine (TPDT) has been determined by the X-ray diffraction of a single crystal; Crystal data were monoclinic, space group P21/c, a= 10.4814(12) Angstrom, b= 5.4203(7) Angstrom, c= 12.3871(17) Angstrom, beta = 107.554 (10)degrees, V= 670.969 Angstrom(3) and Z= 2. The X-ray diffractions of the powder and the thin film of the compound have also been studied at room temperature. Sharp diffraction lines of the thin film with thickness of 500 Angstrom, 100, 200, 500 and 600 lines were found. The TPDT molecules in this film arrange along the a*-axis perpendicular to the substrate. The absorption spectra of several thin films with thickness of 150 Angstrom, 500 Angstrom, 700 Angstrom, 900 Angstrom and 1200 Angstrom have been studied at room temperature. The spectra of thin films were very sensitive to the molecular arrangement. A new sharp absorption band at around 686 nm was observed for the oriented films of the 500 Angstrom, 700 Angstrom and 900 Angstrom. This behavior observed in the oriented film may arise from the Davydov splitting. When the oriented film of TPDT was exposed to bromine gas, the color of the film changed remarkably. Then the new absorption band was observed at around 800 nm. The thin film exposed to bromine gas showed a broad diffraction peak at around 2 theta= 27 degrees. This thin film became mostly amorphous.