The invention discloses a high-opacity white or light flame-retardant polypropylene composition and a preparation method thereof. The high-opacity white or light flame-retardant polypropylene composition comprises, by weight, 35-75 parts of polypropylene resin, 3-5 parts of environment-friendly phosphorus, nitrogen and bromide composite flame retardant, 15-40 parts of opacifying agent A, 0.01-0.1part of opacifying agent B, 0.2-1 part of antioxygen, 0.3-1 part of lubricant and 0.1-1 part of white or light toner. By the aid of the efficient environment-friendly phosphorus, nitrogen and bromidecomposite flame retardant, the composition meets requirements for vertical combustion V2 grade of a UL94 flammability standard, by matching of the opacifying agent A and the opacifying agent B, extremely low transmission of light of the composition is realized, and the composition can be prepared into high white or various light colors. By utilizing the environment-friendly flame retardant, low toxicity and low smoke effects can be realized during combustion, mechanical property of the composition can be kept well, and the composition is applicable to preparation of various white or light products requiring flame retardant and lightproof effects.