The microaggregation and properties of the vertical black soap film (BSF) as well as the BSF-forming aqueous solution containing 10(-2) M cetyltrimethylammonium bromide and 10(-3) M brilliant yellow (BY) have been studied by FTIR and UV-vis spectra, clarifying the self-assembly characteristics of the BSF, which makes the construction of its two surfactant monolayers independent of the thickness of aqueous core and causes the critical temperature of the gel-to-liquid crystal phase transition and the microaggregation of dye molecules in the BSF different from that of the BSF-forming solution. In the liquid crystalline BSF the hydrocarbon chain is averagely oriented with an angle of 44.7 degrees from the surface normal and the order parameter S-mol was calculated to be 0.26, revealing the long-range order of the chain orientation.