The spectral bidirectional reflectance distribution function (spectral BRDF) of mauve and white painted plate are measured in the visible spectrum (400～780 nm). The relationship between variation of spectral BRDF with wavelength and scattering angle and optical characteristics of the measured samples is discussed. With five-parameter model of BRDF and the modified particle swarm optimization (PSO) algorithm, the optimum parameters of the model at each wavelength in the measured spectrum are retrieved at intervals of 1 nm. Spectral BRDF and directional hemisphere reflectance (DHR) of samples calculated with the model are in good agreement with the measured data, which indicates that the means and result of spectral BRDF modeling are doable and reliable. Spectral BRDF of target samples can be used in the research of spectral scattering of objects, which is of great value to the detection, tracking and identification of objects.