The flue gas pollutants deep-removal technology (DRT) focusing on PM_2.5 removal is the prime method of further reducing pollutants emission from coal-fired power plants. In view of the four key technological challenges in developing the DRT, studies were conducted on a series of purification technologies and the DRT was developed and successfully applied in 660 MW and 1000 MW coal-fired units. This paper analyzes the application results of the demonstration project, and proposes a roadmap for the follow-up researches and optimizations.