The invention discloses a nanometer fiber membrane for filter use in a liquid infusion filter device and a preparation method thereof. The preparation method comprises the steps that 1, the polymer and the electrolyte are added into a solvent, then heated at a constant temperature and stirred until the mixture is dissolved, and a polymer spinning silk solution is obtained; 2, the polymer spinning silk solution is defoamed then electrostatically spun to obtained a separation layer; after an anti-bacterial spinning silk solution is defoamed, electrostatic spinning is conducted on the separation layer to obtain the anti-bacterial layer; 3, the electrostatic spinning membrane obtained from step 2 which contains the separation layer and the anti-bacterial layer is subjected to the process of desiccation, hot press and sterilization and disinfection, and the nanometer fiber membrane for filter use in a liquid transfusion filter device with the anti-bacterial function is obtained. The nanometer fiber membrane is simple and easy to achieve in preparation, the inner hole diameter of the membrane can be handily and precisely controlled, the filter of the transfused drug liquid can be satisfied under different conditions, meanwhile industrialized large scale productions are easily achieved.