According to the non-imaging pump style, pump cavity structure with the theoretical maximum coupling efficiency is researched. Multi-lamp non-imaging pump cavities are designed by edge-ray principle and constant string length method. Two calculation models are obtained through the difference of amplifier structures. The Nd∶glass surfaces illumination in the non-imaging and elliptical imaging pump cavity are simulated with the same pump energy. Results show that there are lamp self-absorption and mutualabsorption in the elliptical imaging pump cavity, which affects amplifier′s gain property. To non-imaging pump cavity, the reflector profile avoids light reflecting back to the lamp and reduces the number of reflections. Thus, non-imaging pump cavity can lead to the maximum coupling efficiency and the best pump uniformity.