The use of nanofibers with uniform diameter in the preparation of nanofiber ion exchange membranes for electrodialysis is important for improving the electrodialysis efficiency. In this paper, we calculate a new curve profile of the collector to obtain uniform fiber in an arched multi-nozzle system. Applying the polymer jet calculation model in electrostatic field based on Calculating Fluid Dynamics (CFD), the velocity field distribution in electrospun polymer jet flow system is numerically calculated and based on which the curved isometric surface is determined. The improved equipotential surface distribution in the electrospinning region with a curved collector, which is consistent with the uniform velocity plane, is validated through numerical simulation. An arched multi-nozzle electrospinning system with a curved collector is constructed and the equation of collector curve can be obtained with a specific diameter electrospinning fiber is found. The average diameter of the electrospun fiber obtained in the case of using the curved collector is 131.3 nm ± 2.6 nm, with the average diameter error of the electrospun fiber less than 2%. As a result, a curved collector is proposed which is an effective way to obtain uniform diameter electrospun fibers without additional means in a multi-nozzle electrospinning device.