The invention provides cationic synthetic sperm oil fat liquor and a preparation method thereof. In the fat liquor, synthetic sperm oil, maleic anhydride, epichlorohydrin and quaternization reagent are used as raw materials, maleic anhydride modified synthetic sperm oil is obtained by addition reaction of the synthetic sperm oil and the maleic anhydride; the maleic anhydride modified synthetic sperm oil is added with the epichlorohydrin, and reacts with the quaternization reagent to prepare the cationic synthetic sperm oil fat liquor. By adopting an internal emulsification method, a cationic active group is introduced to the molecular structure of the synthetic sperm oil, so the stability of the emulsion, uniformity and permeability of the fat can be greatly improved, and the cationic synthetic sperm oil fat liquor has better effects of dyeing, burnishing and color fixing than that of the cationic fat liquor by the traditional external emulsification method.