A method for video coding includes encoding or decoding a coding block in a current picture with an affine motion model based inter-picture prediction method in a video coding system, storing affine motion information of the coding block in a history-based motion vector prediction (HMVP) buffer that is configured for storing affine motion information candidates each including affine motion information of a processed affine-coded coding block, and constructing a motion candidate list for a current block that includes at least one candidate selected from the affine motion information candidates stored in the HMVP buffer or derived from one of the affine motion information candidates stored in the HMVP buffer.