The embodiment of the invention provides an encoding method in dynamic power consumption control, and an encoder/decoder. The encoder comprises a control unit, an initial encoding unit and L increment encoding units, wherein the control unit is used for only starting the initial encoding unit to perform the encoding under a RS(N0, K) working mode, or only starting the initial encoding unit and the former j increment encoding units in L increment encoding units to perform the encoding under the RS(Nj, K) working mode; the initial encoding unit is used for performing RS FEC encoding on m(x) to obtain the quotient D0(x) and the residue R0(x) of the xN0-Km(x) relative to the g0(x); the h+1 increment encoding unit is used for obtaining the quotient Dh+1(x) and the residue Rh+1(x) of the xNh+1-Km(x) relative to the gh+1(x) according to the quotient D0(x) and the residue R0(x).