Solid propellant air-turbo-rocket(SPATR) is an air-breathing propulsion system.A numerical model of performance and characteristics analysis for SPATR was presented and the corresponding computer program was written according to the operation characteristics of SPATR.The influence on the SPATR performance at design point caused by the gas generator exit parameters and compressor pressure ratio had been computed and analyzed in detail.The off-design performance of SPATR at sea level and high altitude had also been computed.The performance of thrust and specific impulse for SPATR with different solid propellant had been compared at off-design points

and the off-design performance comparison had been made between fuel-rich and oxygen-rich.The computation results indicated that SPATR operates within wide range of Mach number(0～3) and altitude(0～12 km)

and SPATR possesses high specific thrust(1 200 N/(kg/s)) and high specific impulse(7 000 N/(kg/s)) when fuel-air ratio of combustor equals fuel-air ratio.