Abstract: In response to the emergency power supply requirements for the first-class loads in the mine, and considering the insufficient capacity of the existing diesel generators and the space constraints of the machine room, this paper proposes three sets of emergency power supply expansion and renovation schemes. Through the analysis of technical feasibility, economy and operating costs, the scheme of "reusing 2 units of 1000 kW generators + adding 1 unit of 3000 kW generator" is recommended. Verified by capacity check, the total installed capacity of the modified diesel generators, which is 5000 kW/6250 kVA, can meet the emergency power supply needs of the existing and reserved first-class loads for deep mining, providing a reliable guarantee for the safe production of the mine.