To test the real-time performance of IR camera, seeker and other IR detector systems in lab, the Hardware-in-the-loop (HWIL) Simulation system can be used. The core of HWIL simulation system is IR scene generator. An overview of IR scene generation technologies including resistor array, IR laser diode array projector and light modulation technology etc. is provided. Then the resistor array, which is rapidly developed and most promising, is thoroughly discussed. This includes a discussion of its latest development, key technologies and its future. The performance of some devices is also provided for comparison.