The invention relates to a preparation method of functional regeneration cellulose fiber. The method comprises the following steps that a cellulose solvent is used for dissolving cellulose ester; a functional powder carrier solution is prepared; a strong shearing effect is provided through stirring equipment, so that functional powder and the carrier solution are mixed to prepare functional mother liquid; the functional mother liquid is injected into cellulose spinning liquid in an online adding mode; the spinning liquid is formed into the functional regeneration cellulose fiber through extrusion and solidification forming. The preparation method can solve the problems that in the traditional method, the mixing of the functional powder and the spinning liquid is difficult, and the dispersion is not uniform; the used mother liquid carrier is formed along with fiber coagulation; no additional auxiliary agents enter a solvent and coagulating bath system. The forming method is simple, flexible and efficient; the production of the functional regeneration cellulose fiber can be realized on the basis of the ordinary production line.