The invention discloses a preparation method of an anti-oxidant silver carp liver protein. The method comprises the following steps: (1) adding a degreased silver carp liver to a phosphate buffer for ultrasonic pretreatment, wherein the ultrasonic frequency is 24kHz, the ultrasonic power is 50-100W and the treatment time is 3-7min; (2) carrying out enzyme deactivation treatment and centrifuging to prepare supernate and a residue; (3) taking the supernate for dialysis, carrying out freeze-drying to obtain a buffer extract protein; (4) adding the residue to a NaOH solution for enzyme deactivation through a water bath for 15-25min, centrifuging to prepare secondary supernate, dialyzing the secondary supernate in a Tris-HCl buffer solution of which the pH is 8.0 for 78h, changing dialysate every 8-12h and carrying out freeze-drying to obtain an alkaline extract protein. The silver carp liver protein is prepared by adopting ultrasonic-assisted buffer solution extraction and alkaline extraction, the method is simple in operation, short in treatment time and relatively high in protein yield, and the antioxidant activity of the two obtained proteins is relatively good.