In this paper, a new thin-layer ion-exchange resin phase analytical method is introduced. It is based on that, the bismuthous cation can associate with iodic anions, so as to formed an anion complex [BiI4-] in a strong acidic environments. This anion complex can also exchanges with a weaker anions on the surface active site of anion exchange resin, so that a [R+] [BiI4-] solid phase binary associational system is produced. Owing to the solid system is a great many dispersive particulates, it can be pressed to a thin-layer by press tools of the so called 搕hin-layer resin phase?or 搑esin phase? and using this solid association system spectrophotometry for the determination of trace metals. So it can increase the analytical sensitivity. This association system exhibits maximum absorbance at 460nm, and obeys Beer抯 law over the concentration range 0.01ug/ml~1.20ug/ml of bismuthous(III). It has a molar absorptivity of 7.1×105 [L/mol穋m]. It indicated the resin phase spectrophotometry is a sensitive analytical method for trace bismuthous. It is 18 times higher than routine aqueous spectrophotometry. The relative standard deviations is 1.82% (n=6) for the measurements of 0.5ug/ml Bi(III). The detection limit of Bismuthous(III) is 1.4×10-8mol/L. The method has applied to the analysis Bi(III) in environmental water samples. It is based on that, the bismuthous cation can associate with iodic anions, so as to formed an anion complex [BiI4-] in a strong acidic environments . This anion complex can also exchanges with a weaker anions on the surface active site of anion exchange resin, so that a [R +] [BiI4-] solid phase binary associational system is produced. Owing to the solid system is a great many dispersive particulates , it can be pressed to a thin-layer by press tools of the so called 搕 hin-layer resin phase ™ or 搑 esin phase ™ and using this solid association system spectrophotometry for the determination of trace metals. So it can increase the analytical sensitivity . This association system exhibits maximum absorbance at 460 nm, and obeys Beer’s law over the concentration range of 0.01 ug / ml to 1.20 ug / ml of bismuthous (III). It has a molar absorptivity of 7.1 × 10 5 [L / mol 穋 m] It shows the resin phase spectrophotometry The relative standard deviations are 1.82% (n = 6) for the measurements of 0.5 ug / ml Bi (III). The detection limit of Bismuthous ( III) is 1.4 × 10 -8 mol / L The method has been applied to the analysis Bi (III) in environmental water samples.