The invention discloses a carboxyl functionalized single-walled carbon nanotube modified polypiperazine amide nanofiltration membrane and a preparation method thereof. The membrane is composed of a polysulfone support layer and a modified polypiperazine amide layer. The polypiperazine amide layer is prepared by in situ interfacial polymerization of piperazine hexahydrate and trimesoyl chloride, and the modified polypiperazine amide layer is modified by doping carboxyl functionalized single-walled carbon nanotubes. The used optimized low monomer concentration PIP and TMC form a thin polyamide selection layer on the surface of a polysulfone carrier. The embedding of the nanomaterial can enhance the hydrophilicity and fouling resistance of the membrane, and the carboxyl functionalized single-walled carbon nanotubes form tubular bulges on the membrane surface, thus greatly improving the water flux of the membrane. The prepared novel film nanocomposite membrane material has similar interception performance to the traditional TFC membrane and better penetration performance.