A digital modulation method, comprising: determining to-be-moved constellation points in a rectangular constellation diagram, wherein the rectangular constellation diagram is a constellation diagram generated by performing quadrature amplitude modulation, QAM, on a data bit stream, wherein constellation points in the rectangular constellation diagram are distributed at corresponding coordinate points in a plane rectangular coordinate system, the to-be-moved constellation points comprise S columns of constellation points, in four quadrants of the plane rectangular coordinate system, wherein S is a quantity of to-be-moved columns in each quadrant; dividing to-be-moved constellation points in each of the four quadrants into two constellation point sets according to a horizontal bisector of an area between a horizontal coordinate axis and a straight line corresponding to a maximum absolute value of vertical coordinates in the rectangular constellation diagram; and moving each constellation point set in the four quadrants, to obtain a cross-shaped constellation diagram, wherein a coordinate of a to-be-moved constellation point in the rectangular constellation diagram is represented with (I, Q), and a coordinate of a moved constellation point in the rectangular constellation diagram is represented with (I', Q'); the moving each constellation point set in the first quadrant comprises: if Q>2S, I'=I-8S, Q'=Q-8S; if 0<Q<2S, I'=I-8S, Q'=Q+4S; the moving each constellation point set in the second quadrant comprises: if Q>2S, I'=I+4S, Q'=Q-8S; if 0<Q<2S, I'=I+4S, Q'=Q+4S; the moving each constellation point set in the third quadrant comprises: if 0>Q>-2S, I'=I+8S, Q'=Q-4S; if Q<-2S, I'=I+8S, Q'=Q+8S; the moving each constellation point set in the fourth quadrant comprises: if 0>Q>-2S, I'=I-4S, Q'=Q-4S; if Q<-2S, I'=I-4S, Q'=Q+8S. determining to-be-moved constellation points in a rectangular constellation diagram, wherein the rectangular constellation diagram is a constellation diagram generated by performing quadrature amplitude modulation, QAM, on a data bit stream, wherein constellation points in the rectangular constellation diagram are distributed at corresponding coordinate points in a plane rectangular coordinate system, the to-be-moved constellation points comprise S columns of constellation points, in four quadrants of the plane rectangular coordinate system, wherein S is a quantity of to-be-moved columns in each quadrant; dividing to-be-moved constellation points in each of the four quadrants into two constellation point sets according to a horizontal bisector of an area between a horizontal coordinate axis and a straight line corresponding to a maximum absolute value of vertical coordinates in the rectangular constellation diagram; and moving each constellation point set in the four quadrants, to obtain a cross-shaped constellation diagram, wherein a coordinate of a to-be-moved constellation point in the rectangular constellation diagram is represented with (I, Q), and a coordinate of a moved constellation point in the rectangular constellation diagram is represented with (I', Q'); the moving each constellation point set in the first quadrant comprises: if Q>2S, I'=I-8S, Q'=Q-8S; if 0<Q<2S, I'=I-8S, Q'=Q+4S; if Q>2S, I'=I-8S, Q'=Q-8S; if 0<Q<2S, I'=I-8S, Q'=Q+4S; the moving each constellation point set in the second quadrant comprises: if Q>2S, I'=I+4S, Q'=Q-8S; if 0<Q<2S, I'=I+4S, Q'=Q+4S; if Q>2S, I'=I+4S, Q'=Q-8S; if 0<Q<2S, I'=I+4S, Q'=Q+4S; the moving each constellation point set in the third quadrant comprises: if 0>Q>-2S, I'=I+8S, Q'=Q-4S; if Q<-2S, I'=I+8S, Q'=Q+8S; if 0>Q>-2S, I'=I+8S, Q'=Q-4S; if Q<-2S, I'=I+8S, Q'=Q+8S; the moving each constellation point set in the fourth quadrant comprises: if 0>Q>-2S, I'=I-4S, Q'=Q-4S; if Q<-2S, I'=I-4S, Q'=Q+8S. if 0>Q>-2S, I'=I-4S, Q'=Q-4S; if Q<-2S, I'=I-4S, Q'=Q+8S.