We performed the numerical simulation of edge-define film-fed growth (EFG) to find the appropriate capillary conditions of Ga2O3 melt. Meniscus and capillary rise were considerably affected by the design of the slits in EFG system. As an example, the ratio of the seed crystal and slit width was > 0.72 with the slit width of 4.4 mm. Narrower slit width resulted in higher capillary rise with longer process time compared to wider slit width. Under the conditions consistent with the simulation results, highly crystalline (100) β-Ga2O3 single crystals were successfully achieved.