The present disclosure provides a method for obtaining a size of a transform block, where the method includes: obtaining a dividing manner of an image block; and obtaining size information of a post-dividing transform block according to the dividing manner of the image block and a width and a height of a pre-dividing transform block. By using the method for obtaining a size of a transform block provided in this embodiment of the present disclosure, a size of a transform block may be coded according to a dividing manner of an image block or a height and a width of a pre-dividing transform block, thereby effectively improving coding efficiency.