The aim of this work was to study the influences of the concentration of carboxymethyl chitosan solution and the process parameters of electrospinning on the diameter of the nanofibers. According to the principle of electrostatic spinning, this paper chose 4 influencing factors, including solution concentration, voltage, flow rate and nozzle diameter, and adopted the Box-Behnken design in response surface methodology (RSM) to predict the diameter of carboxymethyl chitosan nanofibers prepared by electrospinning, obtaining a quadratic regression model. The results showed that the concentration, flow rate, quadratic of concentration and quadratic of nozzle diameter had significant influences on the diameter of the nanofibers. There was high consistency between the experimental values and the prediction values. The model obtained through response surface method could not only predict the diameter of carboxymethyl chitosan fibers, but also determined the optimal electrospinning parameters of carboxymethyl chitosan fibers.