Optimization and design of power supply system of fully-mechanized mining equipments in modern mine made a difference in high production and high efficiency. Formulation of power supply system for fully mechanized coal face, equipment load distribution, capacity check of substation, selection check of high voltage explosion proof switch and cable selection were optimized and designed on the basis of theoretical analysis, which guaranteed stability of power supply system in fully mechanized mining face. After its optimization and design, the impact on entire power supply system was little in th process of frequently starting of various equipments, which guranteed power supply quality and normal operation of production system.