The invention discloses a preparation method for a Janus polyvinylidene fluoride (PVDF) separation membrane, and relates to a membrane preparation method. The preparation method for the Janus polyvinylidene fluoride (PVDF) separation membrane aims at solving the problem that the wettability difference of upper and lower surfaces of an existing Janus membrane is small, and therefore high oil-waterseparation efficiency and high fouling resistance performance are achieved. The preparation method comprises the steps that step one, a standard buffering solution is prepared; step two, a dopamine coating solution is prepared; step three, a super-hydrophilic coating is prepared; step four, sacrificial layer liquid is introduced; step five, a PVDF casting membrane solution is prepared; step six, the Janus polyvinylidene fluoride ultrafiltration membrane is prepared, that is to say, the Janus polyvinylidene fluoride (PVDF) separation membrane is obtained. The preparation method has the following advantages that the prepared Janus polyvinylidene fluoride (PVDF) separation membrane takes a non-woven fabric material as a supporting layer and is high in mechanical strength, the upper and lowersurfaces of the membrane are opposite in wettability, the separation membrane is suitable for oil-in-water emulsion separation, the oil-water separation efficiency reaches 99.99%, and the flux recovery rate reaches 90% or above.