Embodiments of the present application relate to a video image encoding method, a video image decoding method, an encoding device, and a decoding device. The method includes: determining a motion vector group of a current encoding block; determining prediction values of a first component set of a motion model initialization vector; determining values of the first component set according to the prediction values of the first component set; and encoding the values of the first component set, and transmitting encoded values of the first component set. According to the video image encoding method in the embodiments of the present application, a motion model initialization vector is determined according to a motion vector group; values of a motion model are determined according to the motion model initialization vector. In this way, a volume of data and a quantity of occupied bits in encoding and decoding transmission can be reduced.