This application provides a method for constructing a motion information list in video encoding and decoding performed by a computer device. The method includes: obtaining a motion information list, which is a candidate motion information list is used for providing a candidate prediction displacement vector; determining at least one piece of motion information when a length of the motion information list meets a condition; and adding the at least one piece of motion information to the candidate motion information list to obtain an updated motion information list when a length of the candidate motion information list is less than a threshold. According to the embodiments of this application, by filling a motion information list using extra motion information when motion information included in the motion information list is insufficient, more effective displacement vectors are provided in the motion information list to achieve a better displacement vector prediction effect.