A video picture coding method, comprising: determining a motion vector difference of an affine picture block; determining motion vector precision of the affine picture block; determining a size of an affine motion compensation picture subblock in the affine picture block according to the motion vector difference, and the motion vector precision, and a distance between control points in the affine picture block, wherein the control points are pixels used to determine the motion vector difference; and performing coding processing on the affine picture block that is divided into one or more of affine motion compensation picture subblocks of the determined size; wherein the determining a motion vector difference of an affine picture block comprises: determining a first component of the motion vector difference according to a difference between motion vectors of a first control point and a second control point that are located on a same horizontal line; and determining a second component of the motion vector difference according to a difference between motion vectors of a third control point and a fourth control point that are located on a same vertical line; wherein a first horizontal distance is a distance between the first control point and the second control point, and a first vertical distance is a distance between the third control point and the fourth control point; and wherein the size is determined according to the first component, the second component, the motion vector precision, the first horizontal distance between the first control point and the second control point, and the first vertical distance between the third control point and the fourth control point. determining a motion vector difference of an affine picture block; determining motion vector precision of the affine picture block; determining a size of an affine motion compensation picture subblock in the affine picture block according to the motion vector difference, and the motion vector precision, and a distance between control points in the affine picture block, wherein the control points are pixels used to determine the motion vector difference; and performing coding processing on the affine picture block that is divided into one or more of affine motion compensation picture subblocks of the determined size; wherein the determining a motion vector difference of an affine picture block comprises: determining a first component of the motion vector difference according to a difference between motion vectors of a first control point and a second control point that are located on a same horizontal line; and determining a second component of the motion vector difference according to a difference between motion vectors of a third control point and a fourth control point that are located on a same vertical line; wherein a first horizontal distance is a distance between the first control point and the second control point, and a first vertical distance is a distance between the third control point and the fourth control point; and wherein the size is determined according to the first component, the second component, the motion vector precision, the first horizontal distance between the first control point and the second control point, and the first vertical distance between the third control point and the fourth control point. determining a first component of the motion vector difference according to a difference between motion vectors of a first control point and a second control point that are located on a same horizontal line; and determining a second component of the motion vector difference according to a difference between motion vectors of a third control point and a fourth control point that are located on a same vertical line; wherein a first horizontal distance is a distance between the first control point and the second control point, and a first vertical distance is a distance between the third control point and the fourth control point; and wherein the size is determined according to the first component, the second component, the motion vector precision, the first horizontal distance between the first control point and the second control point, and the first vertical distance between the third control point and the fourth control point.