The invention discloses a solar-assisted reheat overheating thermal power generation system and an emission reduction dilatation method. The solar-assisted reheat overheating thermal power generation system comprises a boiler, a flue gas overheater, a solar overheater, a solar reheater, a flue gas reheater, a turbine, an electric generator, condensers and a circulating pump. The boiler, the flue gas overheater, the solar overheater, the turbine, the condenser, the other condenser and the boiler are connected in sequence to form a loop. A turbine low-pressure cylinder inlet, the solar reheater, the flue gas reheater and a turbine high-pressure outlet are connected in sequence to form a loop. The turbine is connected with the electric generator. According to the solar-assisted reheat overheating thermal power generation system and the emission reduction dilatation method, solar heat storage heat exchangers serve as the reheaters and the overheaters, the overheating surfaces and the reheating surfaces of an existing thermal power generation system are increased, partial functional replacement of coal by solar energy is achieved, the purposes of emission reduction and dilatation are achieved, and the purposes that the solar energy is economically utilized and emission by existing power stations is lowered are achieved.