The invention provides a preparation method of a dopamine nanofiltration membrane. The method is characterized by comprising the steps that 1, a mixed solution of dopamine and a nucleophilic reagent is prepared, wherein the concentration of the nucleophilic reagent is 0.1 g/L-10 g/L, and the concentration of the dopamine is 0.1 g/L-5 g/L; 2, a basement membrane is immersed into the mixed solution of the dopamine and the nucleophilic reagent and put on a shaking table to vibrate for 5 min to 24 h, after the basement membrane is taken out, the mixed solution on the surface is removed through washing with water, and the basement membrane is air-dried; 3, the air-dried membrane obtained in the step 2 is soaked in 1 wt%-10 wt% of a crosslinking agent solution to react for 5 min to 48 h, the membrane is taken out and then put into a vacuum drying oven, heat treatment is conducted at 30 DGE C to 80 DEG C for 5 min to 12 h, the membrane is taken out, and the dopamine nanofiltration membrane is obtained. According to the preparation method of the dopamine nanofiltration membrane, the auto-agglutination process of the dopamine is regulated and controlled with the nucleophilic reagent, a poly dopamine coating which is large in cross-linking point density is formed in a short time, and the dopamine nanofiltration membrane which is good in separating property is obtained after cross-linking.