Two azo compounds (1: 1-phenylazo-2-naphthol and 2: 1-(2-nitrophenylazo)-2-naphthol) were synthesized by diazo coupling reaction of aniline and o-nitroaniline with 2-naphthol, respectively. Their structures were characterized by IR, and the spectral properties of the compounds were studied by UV spectra. The results showed that the two compounds have big molar absorptivity (1：ε_478nm = 1.49 × 10⁴ L/mol·cm；2：ε_329nm = 1.32 × 10⁴ L/mol·cm). When the pH of the solution is less than 10, the UV spectrum is basically unchanged. In the strong alkaline range, the UV spectrum changes, showing a certain acid-base discoloration.