The invention relates to a nuclear energy and slot-type solar-thermal combined power generation system and a power generation method. The nuclear energy and slot-type solar-thermal combined power generation system comprises a nuclear energy heating circuit, a solar heating circuit and a power generation circuit. The power generation circuit comprises a steam turbine connected with a generator, thesteam inlet of the steam turbine is connected with a steam generator through a superheater, and the steam outlet of the steam turbine is led into the steam generator through a condenser and a water supply circulating pump. The nuclear energy heating circuit is connected to the steam generator for heat exchange, and the nuclear energy heating circuit is provided with a main pump, a nuclear reactorand a voltage stabilizer. The solar heating circuit is connected to the superheater for heat exchange, and the solar heating circuit is provided with a low-temperature molten salt tank, a slot-type solar mirror field and a high-temperature molten salt tank. In the process of power generation, the nuclear energy heating circuit heats the cooling water in the steam generator into saturated steam, wherein the saturated steam is sent into the superheater; and the solar heating circuit heats the saturated steam in the superheater into superheated steam. According to the nuclear energy and slot-type solar-thermal combined power generation system and the power generation method, the risk of molten salt solidification can be reduced, the auxiliary power consumption can be reduced, and the power generation efficiency can be improved.