The invention discloses a nuclear power engine. The nuclear power engine comprises a compression barrel, a rotary barrel, a spherical burner and a main shaft. The compression barrel, the spherical burner and the rotary barrel are sequentially connected in series through the main shaft and are in linkage work. Positive arc vortex blades are arranged in the compression barrel, and reverse arc vortex blades are arranged in the rotary barrel. A controllable spherical nuclear power reactor is arranged in the spherical burner. The portions, connected with the main shaft, of the two sides of the controllable spherical nuclear power reactor are provided with a positive six-process control body and a reverse six-process control body correspondingly, and therefore a flow channel which is periodically opened or closed is formed. The six work processes of gas intake, compression, burning, acting, gas exhausting and gas suction of a heat engine and multiphase nuclear reactions of pre-explosion, fission, fusion, fission and fusion are achieved. The thermal energy flow of the nuclear power engine is applied to an aerospace plane engine or an internal combustion engine or a small-sized novel power generator. By the adoption of the nuclear power engine, the application range of nuclear energy is expanded, nuclear energy utilization becomes general, peaceful and environmentally friendly, and the nuclear energy can better serve human beings.