A simulation method of infrared (IR) detection of midcourse ballistic targets by spaceborne early warning systems is proposed. The IR radiation characteristics of midcourse targets are studied by using the infrared module of Satellite Tool Kit/Electro-Optical Infrared Sensor (STK/EOIR). First, the simulation method of dynamic IR radiation characteristics of midcourse ballistic targets based on STK/EOIR is proposed. The calculation model of IR radiation of EOIR targets and the receiving model of the sensor are analyzed. Then, the simulation results of IR irradiation of a typical target in mid-infrared waveband, mid and long infrared waveband and long infrared waveband are given. Finally, the influences of observation angle and observation range on the target IR irradiation received by spaceborne staring sensors are compared. The simulation results show that the IR radiation intensity of midcourse ballistic targets can meet the detection sensitivity requirements of spaceborne staring sensors.