An inter prediction method includes obtaining predicted motion information of a current image block, where the predicted motion information is used to obtain one or more motion vectors of the current image block, the motion vectors include a forward MV and a backward MV for a bidirectional inter prediction, determining a motion vector difference for the current image block, and calculating the motion vectors based on the predicted motion information and the motion vector difference, where the motion vector difference is shared by the forward MV and the backward MV.