A systematic design of a 100 J/10 Hz multislab Nd:glass laser amplifier is proposed. A four-dimensional numerical model was developed for exploring the influence of amplified spontaneous emission (ASE) on the stored energy of the laser amplifier. The influences of different parameters, including the doping concentration of the gain slab, pump pulse duration ( T p u m p ), and pump energy density ( E p ) absorbed in the gain slab, on the stored energy and storage efficiency were studied in detail. Furthermore, the uniform distribution of the stored energy for a larger aperture of the gain slab and a higher pump energy density of the laser amplifier was determined. In addition, the effects of the slab-to-slab transfer of ASE rays on the stored energy were explored. The results show that the distributions of the stored energy for the 100 J/10 Hz laser amplifier were uniform; furthermore, an average storage efficiency of 60.87% was obtained when the pump energy density absorbed in each slab was 0.9 J / c m 3 and the pump duration was 300 µs.