The invention discloses a preparation method for anionic linear copolymerized organic silicon softening and finishing agent. Under the conditions of high salinity and high alkalinity, cationic groups playing the function of stabilization in the structure of the organic silicon softening and finishing agent are easily flocculated with a dye dispersant, the stability of emulsion is broken, and phenomena like breaking of emulsion and floating of oil are generated. The method comprises organic silicon macromolecule chain extension reaction of 1,1,3,3-tetramethyl disiloxane, addition reaction of 3-chloro-2-methylpropene and terminated hydrogen-containing silicone oil, preparation of terminated chlorine-containing and side-chain hydrogen-containing silicone oil, addition reaction of olefin acid and side-chain hydrogen-containing silicone oil, ammonolysis of an organosilicone macromolecular chain segment, preparation of terminated epoxy-containing polyether, and condensation polymerization of the organosilicone macromolecular chain segment and a polyether chain segment. According to the method, the organosilicone chain segment is subjected to anion modification, the compatibility of the emulsion to anions is improved, the introduction of the anions also greatly improves the high temperature resistance, salt tolerance, alkaline resistance properties of the emulsion, and the product can be suitable for dyeing one-bath processing.