In order to solve the complex problem of the traditional power supply system design method in the design of long-distance power supply system, this paper proposes a design method of long-distance power supply system for fully mechanized mining face based on the limit power supply distance. Taking the power supply system of 11012 fully mechanized mining face in Zhaogu No.2 Coal Mine of Henan Energy Coking Coal Group as an example, this paper expounds the design scheme of long-distance power supply system from the aspects of mobile substation selection, high-voltage cable selection and low-voltage cable selection, and finally forms the design concept and method of long-distance power supply system of fully mechanized mining face based on limit power supply distance.