The invention discloses an antistatic finishing agent for a wool fabric and a preparation method thereof, the preparation method comprises the following steps: taking a polyurethane emulsion, heatingup to 80 to 90 DEG C, dropwise adding a pre-emulsion and an initiator into the polyurethane emulsion, continuing reflux and heat preservation reaction for 2-3h after the completion of the dropwise addition of the pre-emulsion and the initiator, adding citric acid to adjust the pH to 3-4, adding polyethylene glycol-200, stirring for reaction for 1-2h, adjusting to neutral, adding water to dilute, sieving, adding dodecyl diphenyl ether disulfonate ammonia, stirring and mixing uniformly, then cooling to room temperature, and removing air bubbles to obtain the antistatic finishing agent for the wool fabric. The wool fabric after being finished by the antistatic finishing agent has good antistatic property, is easy to process, reduces static electricity generation during use, has good water washing and abrasion resistance, and has a long service life.