Based on the ray tracing method, the design of coupling system for large aperture laser diode (LD) arrays applied in end-pumped solid state laser was investigated systematically. Combming the current hollow duct coupling system for large aperture LD arrays, we discuss the common rules in designing coupling system for large aperture LD arrays from the coupling efficiency, energy distribution and propagation characteristics. Also, a new way to predigest the elements of coupling system for large aperture LD arrays by arranging small arrays spherically was introduced. For 100kW LD arrays, using only one hollow duct we obtained excellent results with large uniform pump field by arranging small arrays spherically, and the intensity was more than 20 kW/cm2 with fluctuation less than 5％. The total coupling efficiency is 98％, and around 90％ of energy was contained within the effective area of gain media.