The embodiment of the invention discloses an image encoding and decoding method and a related device. The image decoding method includes the steps that a current image is acquired, K reference images of the current image are selected from a knowledge base, at least one image in the knowledge base does not belong to the random access fragment where the current image is located, and K is an integer larger than or equal to one; according to the K reference images, the current image is decoded. Due to the technical scheme, video encoding/decoding efficiency can be improved easily.