With the low-cost advantage of relatively abundant coal resources and the characteristics of ensuring the stable operation of the power system, thermal power units have long occupied a dominant position in our country's energy structure. However, with the increasing global attention to climate change and the proposal of China's carbon peaking and carbon neutrality goals, the environmental pressure caused by the "three wastes" generated during the operation of thermal power units has become increasingly prominent. As a result, thermal power units are facing unprecedented pressure on energy conservation and emission reduction. In this context, the energy-saving transformation and optimization and upgrading of thermal power units have become a research hotspot. At present, the research on energy-saving technology of thermal power units in academia and industry mostly focuses on a single technical field or specific application scenarios, and lacks a systematic combing of the latest progress of mainstream technologies, as well as a comprehensive analysis of the application bottlenecks and research gaps of various technologies, which restricts the coordinated development and large-scale application of energy-saving technologies to a certain extent. In view of this, this work takes the energy-saving technology of thermal power units as the research object, and comprehensively sorts out the current mainstream energy-saving technologies. It includes boiler efficient combustion optimization, heating surface cleaning and transformation, turbine flow part upgrade, waste heat recovery and cascade utilization technology, cold end system optimization and other technologies. In order to evaluate the actual value of various technologies more objectively, this work takes the coal consumption rate as the core economic benefit index, combined with the transformation cases and operation data of typical thermal power units at home and abroad, and deeply analyzes the latest research progress, practical application effects, technical advantages and limitations of different energy-saving technologies. The results show that the energy-saving technology of thermal power units has achieved remarkable results in improving energy efficiency and reducing environmental pollution. However, further research and optimization are still needed in the improvement of multi-objective optimization models, intelligent diagnosis and predictive maintenance, and the application of advanced materials to promote the sustainable development of energy-saving technologies for thermal power units.