This paper describes the optical properties of prime-color fluorescent lamps popular in recent years. The main purpose is to improve the luminous efficiency and colorimetrio properties of fluorescent lamps. The prime-color phosphors used in the fluorescent lamps are mixtures of three kinds of phosphors emitting narrow bands of red, green and blue lights respectively. The relative spectral power distribution(SPD) of the prime-color blend of phosphors is a weighted linear combination of the SPD of individual.