Image encoding and decoding methods and related devices are provided. An image encoding and decoding method includes: for a sub-image block obtained by partitioning an image block, determining at least two position parameters, in which the at least two position parameters include a first position parameter and a second position parameter, the first position parameter identifies whether the sub-image block is a rectangle or not a rectangle, and the second position parameter identifies endpoint information of the sub-image block; determining an encoding sequence of the first position parameter and the second position parameter according to a partition manner of the image block; and encoding the at least two position parameters according to the determined encoding sequence.