Neutron production rate in spherically convergent beam fusion(SCBF) device as a portable neutron source strongly depends on the ion current and the grid cathode structure. In this paper, as the process of design and analysis, Design of Experiment(DOE) based on the results by Finite Element Method-Flux Corrected Transport(FEM-FCT) method is employed to calculate the ion current. This method is very useful to find optimal design conditions in a short time. Number of rings, radius of rings, and distance between the grid cathode and center are selected as control factors. From the results in the optimized model, the higher ion current is calculated and deeper potential well is also observed.