The reaction conditions, the spectrophotometric characteristics, and the analytical properties of the ion-association complex of 〔I2Br〕- with the basic triarylmethane dye such as ethyl violet (EV), crystal violet (CV), and victoria blue 4R (VB4R) in the presence of polyvinyl alcohol (PVA) were studied. The results showed that the color of the solutions would change obviously when the above ion-association complexes were formed in dilute phosphoric acid solution. The molar absorptivities (ε) of different systems are between 2.6×104 and 6.2×104 L*mol-1*cm-1. The sensitivity of the ethyl violet system is the highest among them. Beer′s law is obeyed in the range of 0～1.6　mg/L　I-　for ethyl violet system, 0～1.4　mg/L for crystal violet system, and 0～0.8 mg/L I- for victoria blue 4R system, respectively. The method can be applied to direct determination of iodide in aqueous solution. The method has good selectivity. A large amounts of halide ions, some other inorganic acid group ions and amount of common metal ions don′t interfere the determination of I-. This method was used to determine I- in kelp, laver and soy bean with satisfactory results