The invention provides a composite polyamide film with salt concentration responsiveness, a preparation method and use of the composite polyamide film, and belongs to the technical filed of compositefilm preparation. The preparation method of the composite film comprises the following steps that (1), a support layer is fixed in a glass plate and a Teflon frame, aqueous phase monomer solution is poured into the Teflon frame, the support layer is soaked for 1-10 minutes; (2), the aqueous phase monomer solution is outwelled, surface moisture of the support layer is removed, then oil phase monomer solution is poured into the surface of the support layer, interface polymerization reaction is conducted for 30-600s; and (3), the oil phase monomer solution is outwelled, the prepared composite polyamide film is placed in distilled water at 4 DEG C to be saved. According to the composite polyamide film, the peculiar salt concentration response characteristics is provided, water flux of the composite polyamide film can increase with increase of salt concentration in raw material solution. Small organic molecules such as salt and dye in the raw material solution can be effectively separated,and very high separation efficiency is provided.