Abstract: Natural gas combined cycle power generation has become a vital pillar of clean power systems due to its advantages of high thermal efficiency and low carbon emissions. This paper analyzes the core factors affecting unit thermal efficiency from three perspectives: gas turbine inlet temperature and compression ratio, thermodynamic losses of heat recovery steam generators (HRSG), and work efficiency of steam turbines. Three key technologies are proposed, including combustion temperature elevation, optimization of triple-pressure reheat waste heat recovery, and cold-end vacuum improvement. Simulation is adopted to quantify the benefits of retrofitting. Comprehensive retrofitting can raise the overall unit thermal efficiency by 2.2 percentage points. Taking Unit 3 of Huadian Banshan Power Generation Co., Ltd. in Hangzhou as an example, the thermal efficiency increases from 55.60% to 56.86% after retrofitting, while the heat rate drops by 144.21 kJ/(kW·h), delivering remarkable energy-saving effects. Multi-link collaborative optimization serves as an effective method to boost thermal efficiency, which can provide references for retrofitting similar generating units.