The problems of the amplitude spatial light modulator(SLM) by electrical addressing in high power laser systems are analyzed. Firstly, the effect of the black gate of the SLM by electrical addressing on the near-field beam shaping is analyzed theoretically. The technical scheme of obtaining the best shaping effect by optimizing the aperture size of the spatial filter is proposed, and the energy efficiency of the filter is calculated. Meanwhile, the effect of liquid crystal SLM′s opening ratio on beam shaping is analyzed. In order to enhance the near-field shaping accuracy, the opening ratio of the SLM should be better than 64%. Finally, the phase distortion introduced by the pure amplitude spatial light modulator is studied. The additional phase is obtained from the theoretical analysis and experimental verification. The calculated maximum additional phase is 0.135λ, which means that the influence on the laser device is within acceptable range.