A new soluble subphthalocyanine (bromoboron trineopentoxy-subphthalocyanine) thin film was prepared by spin-coating on a single-crystal silicon substrate. The ellipsometric spectra of this film were investigated with an improved automatic ellipsometer. The complex refractive index, dielectric functions and absorption coefficient of this film in the 300～800 nm wavelength region were given. The spectra were explained and discussed as well.