The invention provides a motion prediction method First, a coding unit (CU) of a current picture is processed, wherein the CU comprises at least a first prediction unit (PU) and a second PU. A second candidate set comprising a plurality of motion parameter candidates for the second PU is then determined, wherein at least a motion parameter candidate in the second candidate set is derive from a motion parameter predictor for a previously coded PU of the current picture, and the second candidate set is different from a first candidate set comprising a plurality of motion parameter candidates for the first PU. A motion parameter candidate is then selected from the second candidate set as a motion parameter predictor for the second PU. Finally, predicted samples are then generated from the motion parameter predictor of the second PU partition.