Arsenic is a toxic metal element and the establishment of a highly sensitive and selective method for As has great significance to human health and environment protection. In sulfuric acid medium, As(Ⅲ) was reduced by NaBH4 to form AsH3 gas that was trapped by the Ce(Ⅳ)-I－ catalytic absorption solution to cause Ce(Ⅳ) concentration decreased and As particle increased, which resulted in the resonance Rayleigh scattering (RRS) and fluorescence increased at 370 and 351 nm respectively. The increased RRS and fluorescence intensities were linear to As(Ⅲ) concentration in the range of 0.006~0.76 and 0.006~0.28 mg·L-1 respectively, with a detection of As of 3.0 μg·L-1 . The new hydride generation-catalytic RRS method was applied for detection of trace As(Ⅲ) in milk samples, and the results were in agreement with that of hydride generation-atomic absorption spectrometry.