Embodiments of the present application provide an inter prediction method, an encoder, a decoder, and a storage medium. The method comprises: determining a prediction mode parameter of a current block; when the prediction mode parameter indicates that the current block determines an inter prediction value by using a geometrical partition mode (GPM), constructing a merge candidate list of the current block; constructing a GPM motion information candidate list according to first motion information in the merge candidate list of the current block; and determining an inter prediction value of the current block according to the GPM motion information candidate list.