The invention provides a method for preparing a cellulose based nano-composite fiber membrane through electrostatic spinning and relates to a preparation method of membranes. The invention aims at solving the problems that formation of a PS (poly styrene) fiber membrane is difficult and compatibility of non-polar PS and polar CNCs is poor in the prior art. The method for preparing the cellulose based nano-composite fiber membrane through electrostatic spinning comprises the following steps: preparing CNCs crystals; adding PS particles into a solvent, sealing, and stirring to obtain a uniform and transparent solution, standing at room temperature, adding the CNCs crystals and Tween 80, and stirring to obtain an electrospinning liquid; putting the electrospinning liquid into a medical injector, connecting the top of the injector with a spraying needle, carrying out electrospinning while a distance between a positive electrode and a negative electrode is fixed, and obtaining the cellulose based nano-composite fiber membrane on an aluminium foil. By adopting the method provided by the invention, the problems that PS membrane formation is difficult and properties can not be easily controlled are solved. The invention belongs to the field of preparation of composite membranes.