Embodiments of a picture prediction method and a related apparatus are disclosed. A picture prediction method includes: determining K1 pixel samples in a picture block x, and determining a candidate motion information unit set corresponding to each pixel sample in the K1 pixel samples, where the candidate motion information unit set corresponding to each pixel sample includes at least one candidate motion information unit; determining a merged motion information unit set i including K1 motion information units, where each motion information unit in the merged motion information unit set i is selected from at least a part of motion information units in candidate motion information unit sets corresponding to different pixel samples in the K1 pixel samples; and predicting a pixel value of the picture block x by using a non-translational motion model and the merged motion information unit set i.