Using the ray tracing and Monte Carlo as well as the experimental fitting data, we present a numerical simulation model for pumping cavities of the multisegment Nd:glass amplifier. The simulation shows that the transfer efficiency, stored energy density distribution and uniformity of the pump radiation are dependent on the pumping cavity geometry. A novel pumping cavity is proposed, which demonstrates advantages of the high efficiency, good uniformity and tolerable cost. The results obtained are useful for the design of the large scale multisegment Nd:glass amplifier.