The invention discloses a method for preparing CA (cellulose acetate) nanofiber composite. The method includes the following steps: preparing a CA solution; adding zinc salt and ferric salt; preparing a gelatin solution; adding copper salt and zinc salt; performing double-nozzle electrostatic spinning by adopting the CA solution and gelatin solution as the spinning solution; uniformly coating at least one surface of the structural layer fiber fabric with the spinning solution; then placing the fabric in glutaraldehyde steam for fumigation; carrying out fluoridation so as to obtain the CA nanofiber composite. According to the invention, the raw materials are easy to obtain, firstly, CA and the gelatin are combined, and then through fluorination, so that the nanofiber composite keeps higher mechanical strength, excellent heat stability and weather resistance, in addition, the combination of CA with gelatin achieves higher porosity as well as good light transmission and ventilation, so that the composite is good in affinity with the human body, is environment-friendly, can efficiently obstruct ultrafine particles, and has great application and industrialization value.