The theoretical and experimental research on high power slab laser with dual doped concentration are conducted. By means of segmented doping, the non-uniformity in absorption pumping power density along the length of laser slab is effectively reduced, the average energy-storage density of single laser slab is obviously enhanced, and the total energy-storage increases by 39%. When the total pumping power of the diode is 15 kW, after passing through the dual doped laser slab, the 3 kW seed light source can extract a power of 5.16 kW, which increases by 36% if compared with that for single doped laser slab. The optical-to-optical conversion efficiency is 34.4%, which is basically consistent with the theoretical prediction.