Abstract: Air turbo rocket (ATR) engines, which are usually used as the power of independent air-launch platforms and near-space aircraft, have been developed for decades. This paper presents an overview of the research progress of ATR engines first. Then the effects of key parameters on the thermodynamic process of ATR engines are investigated. These parameters are the temperature ratio in the gas generator, the pressure ratio in the compressor, and the pressure ratio in the turbine. On this basis, the overall performance of ATR engines with monopropellant and bipropellant is studied through numerical simulations and experiments. By analyzing the start-up and operation characteristics under a high-attitude working condition, it is found that large thrust and short start-up time (less than five seconds) can be obtained in flight envelopes with the Mach number less than four. To increase the velocity range and reduce the fuel consumption of ATR engines, an innovative scheme integrating the ATR engine and the scramjet engine is proposed. This combined-cycle engine takes full advantage of ATR’s good acceleration ability and scramjet’s hypersonic cruise capability. Results show that continuous thrust can be obtained during the mode transition between the ATR and ramjet, providing a prospective power solution for supersonic and hypersonic near-space aircraft.