The invention discloses an energy saving system for enabling thermal power plant boiler flue gas waste heat to be used for central heating, and belongs to the technical field of thermal power plant boiler flue gas waste heat recycling and utilization. Recycled waste heat is directly used for a central heating system. Flue gas waste heat recycling of the flue gas waste heat recycling system is divided into two processes. At first, the heat of high-temperature water which is formed through direct contact heat exchange between desulfurization slurry and flue gas in a wet type desulfurization tower is recycled, adopted equipment is an absorption type heat pump, and high-level driving energy comes from turbine extraction steam; heat supply return water is heated once through the heat pump and then enters a gas-water heat exchanger arranged in front of a dust remover, an S-shaped pipeline with the insufficient length is arranged in the gas-water heat exchanger, and the heat supply return water flows in the pipeline to absorb high-temperature flue gas waste heat so as to be further heated. At the moment, if the water temperature can meet heating network requirements, water does not need to enter a heating network heater; and if not, water enters the heating network low-voltage heater to be heated to reach the temperature needed by a heating network. By means of the system, energy consumption of a thermal power plant is reduced, the energy utilization efficiency is improved, and environmental influence of the thermal power plant is reduced.