The hollow lens duct is introduced for the application in the coupling of pump radiation from extended two-dimensional semiconductor laser diode arrays into solid state laser gain media. With the help of numerical analysis of three-dimension ray tracing, a computer simulation program for longitudinal-pump laser diode (LD) coupling system was developed. Based on the result of simulation, a coupling system for large-aperture high-power LD arrays using hollow lens duct was build. Coupling efficiency beyond 90% was reached with perfect pumping-uniformity on the surface of gain material. An experience formula for hollow lens duct design was deduced at the same time, it would be very helpful in designing coupling system of large-scale diode-pumped solid-state lasers (DPSSLs).