To satisfy development and test of infrared seeker, a modeling method of four-element infrared detection system was propose, which was achieved by combination of computer simulation and hardware platform. The dynamic information generated by model calculation was composed of target movement, release of jamming projectile and noises, the hardware platform generated four real-time pulses which simulated output of the coordinator in real environment. A test-platform was provided for seeker to verify and modify the algorithms of tracking and anti jamming. The working principles of four-element infrared detection system and the method of software simulation and hardware implementation were described.