Embodiments of the present invention provide an intra-frame decoding method and apparatus for a signal component sampling point of an image block. The method includes: obtaining prediction mode information about a first signal component of a current block from a video code stream; determining a prediction mode for the first signal component of the current block, where the prediction mode for the first signal component of the current block is one of a DM mode and an LM mode; obtaining a prediction value of a first signal component sampling point of the current block according to the prediction mode for the first signal component of the current block; and obtaining a reconstruction value of the first signal component sampling point of the current block. The technical solutions provided by the embodiments of the present invention reduce complexity of implementing a decoding end.