The disclosure discloses a method for processing video signals and an apparatus therefor. Specifically, the method of processing video signals based on history based motion vector prediction, comprising: configuring a merge candidate list based on a neighboring block to a current block; adding a history based merge candidate of the current block to the merge candidate list when a number of merge candidates included in the merge candidate list is smaller than a first predetermined number; adding a zero motion vector to the merge candidate list when the number of merge candidates included in the merge candidate list is smaller than a second predetermined number; obtaining a merge index indicating a merge candidate used for inter prediction of the current block in the merge candidate list; generating a prediction sample of the current block based on motion information of the merge candidate indicated by the merge index; and updating a history based merge candidate list based on the motion information.