Embodiments of the present invention provide an encoding or decoding method and apparatus. The method includes: extracting first information in a bitstream; determining a chroma component intra prediction mode according to the first information; when the chroma component intra prediction mode cannot be determined according to the first information, extracting second information in the bitstream; and determining the chroma component intra prediction mode according to the second information, where the first information includes information for indicating whether the chroma component intra prediction mode is a DM mode or an LM mode, the second information is used to indicate a remaining mode as the chroma component intra prediction mode, and the remaining mode is one of available chroma component intra prediction modes other than a mode that may be determined according to the first information.