The invention relates to a nanofiltration membrane for a one-piece intelligent water purification faucet and a preparation method thereof. The nanofiltration membrane is composed of the following layers in sequence: a nonwoven supportive base layer with a thickness of 10-70 [mu]m, a polymer supportive middle layer with a thickness of 10-30 [mu]m, and a compact separation layer surface layer with a thickness of 30-100 nm. The provided nanofiltration membrane has an ultrahigh throughput and high hardness elimination rate under an ultralow pressure condition; can realize structure performance response to change the water yield and water quality according to the change of environment, and satisfies the requirements of users on water yield and water quality. The produced nanofiltration membrane can better meet the requirements of households on the water purification membranes, and has a good application prospect.